Delegate network tile fetching to NetworkTileProvider

Replace our custom tile pipeline (fetchRemoteTile / _SimpleSemaphore /
exponential backoff) with flutter_map's built-in NetworkTileProvider,
gaining persistent disk cache, ETag revalidation, RetryClient, and
obsolete request aborting for free.

DeflockTileProvider now extends NetworkTileProvider and overrides
getTileUrl() to route through TileType.getTileUrl() (quadkey,
subdomains, API keys). getImageWithCancelLoadingSupport() routes
between two paths at runtime: the common network path (super) when
no offline areas exist, and a DeflockOfflineTileImageProvider for
offline-first when they do.

- Delete tiles_from_remote.dart (semaphore, retry loop, spatial helpers)
- Simplify MapDataProvider._fetchRemoteTileFromCurrentProvider to plain
  http.get (only used by offline area downloader now)
- Remove dead clearTileQueue/clearTileQueueSelective from MapDataProvider
- Remove 7 tile fetch constants from dev_config.dart
- TileLayerManager now disposes provider on cache clear and uses actual
  urlTemplate for cache key generation
- 9 new tests covering URL delegation, routing, and equality

Closes #87 Phase 2.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/services/map_data_submodules/tiles_from_local.dart

@@ -4,11 +4,21 @@ import '../offline_areas/offline_area_models.dart';
 import '../offline_areas/offline_tile_utils.dart';
 import '../../app_state.dart';
 
-/// Fetch a tile from the newest offline area that matches the current provider, or throw if not found.
-Future<List<int>> fetchLocalTile({required int z, required int x, required int y}) async {
+/// Fetch a tile from the newest offline area that matches the given provider, or throw if not found.
+///
+/// When [providerId] and [tileTypeId] are supplied the lookup is pinned to
+/// those values (avoids a race when the user switches provider mid-flight).
+/// Otherwise falls back to the current AppState selection.
+Future<List<int>> fetchLocalTile({
+  required int z,
+  required int x,
+  required int y,
+  String? providerId,
+  String? tileTypeId,
+}) async {
   final appState = AppState.instance;
-  final currentProvider = appState.selectedTileProvider;
-  final currentTileType = appState.selectedTileType;
+  final currentProviderId = providerId ?? appState.selectedTileProvider?.id;
+  final currentTileTypeId = tileTypeId ?? appState.selectedTileType?.id;
   
   final offlineService = OfflineAreaService();
   await offlineService.ensureInitialized();
@@ -20,7 +30,7 @@ Future<List<int>> fetchLocalTile({required int z, required int x, required int y
     if (z < area.minZoom || z > area.maxZoom) continue;
     
     // Only consider areas that match the current provider/type
-    if (area.tileProviderId != currentProvider?.id || area.tileTypeId != currentTileType?.id) continue;
+    if (area.tileProviderId != currentProviderId || area.tileTypeId != currentTileTypeId) continue;
 
     // Get tile coverage for area at this zoom only
     final coveredTiles = computeTileList(area.bounds, z, z);
@@ -35,7 +45,7 @@ Future<List<int>> fetchLocalTile({required int z, required int x, required int y
     }
   }
   if (candidates.isEmpty) {
-    throw Exception('Tile $z/$x/$y from current provider ${currentProvider?.id}/${currentTileType?.id} not found in any offline area');
+    throw Exception('Tile $z/$x/$y from provider $currentProviderId/$currentTileTypeId not found in any offline area');
   }
   candidates.sort((a, b) => b.modified.compareTo(a.modified)); // newest first
   return await candidates.first.file.readAsBytes();

lib/services/map_data_submodules/tiles_from_remote.dart

@@ -1,265 +0,0 @@
-import 'dart:math';
-import 'dart:io';
-import 'dart:async';
-import 'package:flutter/foundation.dart';
-import 'package:latlong2/latlong.dart';
-import 'package:flutter_map/flutter_map.dart';
-import 'package:deflockapp/dev_config.dart';
-import 'package:deflockapp/services/http_client.dart';
-
-/// Global semaphore to limit simultaneous tile fetches
-final _tileFetchSemaphore = _SimpleSemaphore(kTileFetchConcurrentThreads);
-
-/// Clear queued tile requests when map view changes significantly
-void clearRemoteTileQueue() {
-  final clearedCount = _tileFetchSemaphore.clearQueue();
-  // Only log if we actually cleared something significant
-  if (clearedCount > 5) {
-    debugPrint('[RemoteTiles] Cleared $clearedCount queued tile requests');
-  }
-}
-
-/// Clear only tile requests that are no longer visible in the given bounds
-void clearRemoteTileQueueSelective(LatLngBounds currentBounds) {
-  final clearedCount = _tileFetchSemaphore.clearStaleRequests((z, x, y) {
-    // Return true if tile should be cleared (i.e., is NOT visible)
-    return !_isTileVisible(z, x, y, currentBounds);
-  });
-  
-  if (clearedCount > 0) {
-    debugPrint('[RemoteTiles] Selectively cleared $clearedCount non-visible tile requests');
-  }
-}
-
-/// Calculate retry delay using configurable backoff strategy.
-/// Uses: initialDelay * (multiplier ^ (attempt - 1)) + randomJitter, capped at maxDelay
-int _calculateRetryDelay(int attempt, Random random) {
-  // Calculate exponential backoff
-  final baseDelay = (kTileFetchInitialDelayMs * 
-    pow(kTileFetchBackoffMultiplier, attempt - 1)).round();
-  
-  // Add random jitter to avoid thundering herd
-  final jitter = random.nextInt(kTileFetchRandomJitterMs + 1);
-  
-  // Apply max delay cap
-  return (baseDelay + jitter).clamp(0, kTileFetchMaxDelayMs);
-}
-
-/// Convert tile coordinates to lat/lng bounds for spatial filtering
-class _TileBounds {
-  final double north, south, east, west;
-  _TileBounds({required this.north, required this.south, required this.east, required this.west});
-}
-
-/// Calculate the lat/lng bounds for a given tile
-_TileBounds _tileToBounds(int z, int x, int y) {
-  final n = pow(2, z);
-  final lon1 = (x / n) * 360.0 - 180.0;
-  final lon2 = ((x + 1) / n) * 360.0 - 180.0;
-  final lat1 = _yToLatitude(y, z);
-  final lat2 = _yToLatitude(y + 1, z);
-  
-  return _TileBounds(
-    north: max(lat1, lat2),
-    south: min(lat1, lat2),
-    east: max(lon1, lon2),
-    west: min(lon1, lon2),
-  );
-}
-
-/// Convert tile Y coordinate to latitude
-double _yToLatitude(int y, int z) {
-  final n = pow(2, z);
-  final latRad = atan(_sinh(pi * (1 - 2 * y / n)));
-  return latRad * 180.0 / pi;
-}
-
-/// Hyperbolic sine function: sinh(x) = (e^x - e^(-x)) / 2
-double _sinh(double x) {
-  return (exp(x) - exp(-x)) / 2;
-}
-
-/// Check if a tile intersects with the current view bounds
-bool _isTileVisible(int z, int x, int y, LatLngBounds viewBounds) {
-  final tileBounds = _tileToBounds(z, x, y);
-  
-  // Check if tile bounds intersect with view bounds
-  return !(tileBounds.east < viewBounds.west ||
-           tileBounds.west > viewBounds.east ||
-           tileBounds.north < viewBounds.south ||
-           tileBounds.south > viewBounds.north);
-}
-
-
-
-final _tileClient = UserAgentClient();
-
-/// Fetches a tile from any remote provider with unlimited retries.
-/// Returns tile image bytes. Retries forever until success.
-/// Brutalist approach: Keep trying until it works - no arbitrary retry limits.
-Future<List<int>> fetchRemoteTile({
-  required int z,
-  required int x,
-  required int y,
-  required String url,
-}) async {
-  int attempt = 0;
-  final random = Random();
-  final hostInfo = Uri.parse(url).host; // For logging
-
-  while (true) {
-    await _tileFetchSemaphore.acquire(z: z, x: x, y: y);
-    try {
-      // Only log on first attempt
-      if (attempt == 0) {
-        debugPrint('[fetchRemoteTile] Fetching $z/$x/$y from $hostInfo');
-      }
-      attempt++;
-      final resp = await _tileClient.get(Uri.parse(url));
-      
-      if (resp.statusCode == 200 && resp.bodyBytes.isNotEmpty) {
-        // Success!
-        if (attempt > 1) {
-          debugPrint('[fetchRemoteTile] SUCCESS $z/$x/$y from $hostInfo after $attempt attempts');
-        }
-        return resp.bodyBytes;
-      } else {
-        debugPrint('[fetchRemoteTile] FAIL $z/$x/$y from $hostInfo: code=${resp.statusCode}, bytes=${resp.bodyBytes.length}');
-        throw HttpException('Failed to fetch tile $z/$x/$y from $hostInfo: status ${resp.statusCode}');
-      }
-    } catch (e) {
-      // Calculate delay and retry (no attempt limit - keep trying forever)
-      final delay = _calculateRetryDelay(attempt, random);
-      if (attempt == 1) {
-        debugPrint("[fetchRemoteTile] Attempt $attempt for $z/$x/$y from $hostInfo failed: $e. Retrying in ${delay}ms.");
-      } else if (attempt % 10 == 0) {
-        // Log every 10th attempt to show we're still working
-        debugPrint("[fetchRemoteTile] Still trying $z/$x/$y from $hostInfo (attempt $attempt). Retrying in ${delay}ms.");
-      }
-      await Future.delayed(Duration(milliseconds: delay));
-    } finally {
-      _tileFetchSemaphore.release(z: z, x: x, y: y);
-    }
-  }
-}
-
-/// Legacy function for backward compatibility
-@Deprecated('Use fetchRemoteTile instead')
-Future<List<int>> fetchOSMTile({
-  required int z,
-  required int x,
-  required int y,
-}) async {
-  return fetchRemoteTile(
-    z: z,
-    x: x,
-    y: y,
-    url: 'https://tile.openstreetmap.org/$z/$x/$y.png',
-  );
-}
-
-/// Enhanced tile request entry that tracks coordinates for spatial filtering
-class _TileRequest {
-  final int z, x, y;
-  final VoidCallback callback;
-  
-  _TileRequest({required this.z, required this.x, required this.y, required this.callback});
-}
-
-/// Spatially-aware counting semaphore for tile requests with deduplication
-class _SimpleSemaphore {
-  final int _max;
-  int _current = 0;
-  final List<_TileRequest> _queue = [];
-  final Set<String> _inFlightTiles = {}; // Track in-flight requests for deduplication
-  _SimpleSemaphore(this._max);
-
-  Future<void> acquire({int? z, int? x, int? y}) async {
-    // Create tile key for deduplication  
-    final tileKey = '${z ?? -1}/${x ?? -1}/${y ?? -1}';
-    
-    // If this tile is already in flight, skip the request
-    if (_inFlightTiles.contains(tileKey)) {
-      debugPrint('[SimpleSemaphore] Skipping duplicate request for $tileKey');
-      return;
-    }
-    
-    // Add to in-flight tracking
-    _inFlightTiles.add(tileKey);
-    
-    if (_current < _max) {
-      _current++;
-      return;
-    } else {
-      // Check queue size limit to prevent memory bloat
-      if (_queue.length >= kTileFetchMaxQueueSize) {
-        // Remove oldest request to make room
-        final oldRequest = _queue.removeAt(0);
-        final oldKey = '${oldRequest.z}/${oldRequest.x}/${oldRequest.y}';
-        _inFlightTiles.remove(oldKey);
-        debugPrint('[SimpleSemaphore] Queue full, dropped oldest request: $oldKey');
-      }
-      
-      final c = Completer<void>();
-      final request = _TileRequest(
-        z: z ?? -1, 
-        x: x ?? -1, 
-        y: y ?? -1, 
-        callback: () => c.complete(),
-      );
-      _queue.add(request);
-      await c.future;
-    }
-  }
-
-  void release({int? z, int? x, int? y}) {
-    // Remove from in-flight tracking
-    final tileKey = '${z ?? -1}/${x ?? -1}/${y ?? -1}';
-    _inFlightTiles.remove(tileKey);
-    
-    if (_queue.isNotEmpty) {
-      final request = _queue.removeAt(0);
-      request.callback();
-    } else {
-      _current--;
-    }
-  }
-
-  /// Clear all queued requests (call when view changes significantly)
-  int clearQueue() {
-    final clearedCount = _queue.length;
-    _queue.clear();
-    _inFlightTiles.clear(); // Also clear deduplication tracking
-    return clearedCount;
-  }
-  
-  /// Clear only tiles that don't pass the visibility filter
-  int clearStaleRequests(bool Function(int z, int x, int y) isStale) {
-    final initialCount = _queue.length;
-    final initialInFlightCount = _inFlightTiles.length;
-    
-    // Remove stale requests from queue
-    _queue.removeWhere((request) => isStale(request.z, request.x, request.y));
-    
-    // Remove stale tiles from in-flight tracking
-    _inFlightTiles.removeWhere((tileKey) {
-      final parts = tileKey.split('/');
-      if (parts.length == 3) {
-        final z = int.tryParse(parts[0]) ?? -1;
-        final x = int.tryParse(parts[1]) ?? -1;
-        final y = int.tryParse(parts[2]) ?? -1;
-        return isStale(z, x, y);
-      }
-      return false;
-    });
-    
-    final queueClearedCount = initialCount - _queue.length;
-    final inFlightClearedCount = initialInFlightCount - _inFlightTiles.length;
-    
-    if (queueClearedCount > 0 || inFlightClearedCount > 0) {
-      debugPrint('[SimpleSemaphore] Cleared $queueClearedCount stale queue + $inFlightClearedCount stale in-flight, kept ${_queue.length}');
-    }
-    
-    return queueClearedCount + inFlightClearedCount;
-  }
-}