refactor: remove cloud save feature entirely

This feature was deemed unnecessary and was adding complexity to the app.

Removed:
- lib/services/cloud_upload_service.dart
- lib/providers/upload_queue_provider.dart
- lib/screens/settings/cloud_settings_page.dart
- lib/screens/settings/widgets/ (cloud status hero card)
- All cloud* settings from AppSettings model
- All cloud-related localization keys (~70 keys)
- Cloud settings from settings_provider.dart
- Cloud menu item from settings_tab.dart
- Cloud upload trigger from download_queue_provider.dart

Dependencies removed:
- webdav_client: ^1.2.2
- dartssh2: ^2.13.0

CHANGELOG updated to remove all cloud save references.

lib/models/settings.dart

@@ -37,15 +37,6 @@ class AppSettings {
   final bool autoExportFailedDownloads; // Auto export failed downloads to TXT file
   final String downloadNetworkMode; // 'any' = WiFi + Mobile, 'wifi_only' = WiFi only
   
-  // Cloud Upload Settings
-  final bool cloudUploadEnabled; // Enable auto-upload after download
-  final String cloudProvider; // 'none', 'webdav', 'sftp', 'gdrive'
-  final String cloudServerUrl; // WebDAV/SFTP server URL
-  final String cloudUsername; // Server username
-  final String cloudPassword; // Server password (stored securely)
-  final String cloudRemotePath; // Remote folder path (e.g. /Music/SpotiFLAC)
-  final bool cloudAllowInsecureHttp; // Allow HTTP for WebDAV (insecure)
-  
   // Local Library Settings
   final bool localLibraryEnabled; // Enable local library scanning
   final String localLibraryPath; // Path to scan for audio files
@@ -84,14 +75,6 @@ class AppSettings {
     this.useAllFilesAccess = false,
     this.autoExportFailedDownloads = false,
     this.downloadNetworkMode = 'any',
-    // Cloud Upload defaults
-    this.cloudUploadEnabled = false,
-    this.cloudProvider = 'none',
-    this.cloudServerUrl = '',
-    this.cloudUsername = '',
-    this.cloudPassword = '',
-    this.cloudRemotePath = '/Music/SpotiFLAC',
-    this.cloudAllowInsecureHttp = false,
     // Local Library defaults
     this.localLibraryEnabled = false,
     this.localLibraryPath = '',
@@ -132,14 +115,6 @@ class AppSettings {
     bool? useAllFilesAccess,
     bool? autoExportFailedDownloads,
     String? downloadNetworkMode,
-    // Cloud Upload
-    bool? cloudUploadEnabled,
-    String? cloudProvider,
-    String? cloudServerUrl,
-    String? cloudUsername,
-    String? cloudPassword,
-    String? cloudRemotePath,
-    bool? cloudAllowInsecureHttp,
     // Local Library
     bool? localLibraryEnabled,
     String? localLibraryPath,
@@ -178,15 +153,6 @@ class AppSettings {
       useAllFilesAccess: useAllFilesAccess ?? this.useAllFilesAccess,
       autoExportFailedDownloads: autoExportFailedDownloads ?? this.autoExportFailedDownloads,
       downloadNetworkMode: downloadNetworkMode ?? this.downloadNetworkMode,
-      // Cloud Upload
-      cloudUploadEnabled: cloudUploadEnabled ?? this.cloudUploadEnabled,
-      cloudProvider: cloudProvider ?? this.cloudProvider,
-      cloudServerUrl: cloudServerUrl ?? this.cloudServerUrl,
-      cloudUsername: cloudUsername ?? this.cloudUsername,
-      cloudPassword: cloudPassword ?? this.cloudPassword,
-      cloudRemotePath: cloudRemotePath ?? this.cloudRemotePath,
-      cloudAllowInsecureHttp:
-          cloudAllowInsecureHttp ?? this.cloudAllowInsecureHttp,
       // Local Library
       localLibraryEnabled: localLibraryEnabled ?? this.localLibraryEnabled,
       localLibraryPath: localLibraryPath ?? this.localLibraryPath,

lib/models/settings.g.dart

@@ -42,14 +42,6 @@ AppSettings _$AppSettingsFromJson(Map<String, dynamic> json) => AppSettings(
   autoExportFailedDownloads:
       json['autoExportFailedDownloads'] as bool? ?? false,
   downloadNetworkMode: json['downloadNetworkMode'] as String? ?? 'any',
-  cloudUploadEnabled: json['cloudUploadEnabled'] as bool? ?? false,
-  cloudProvider: json['cloudProvider'] as String? ?? 'none',
-  cloudServerUrl: json['cloudServerUrl'] as String? ?? '',
-  cloudUsername: json['cloudUsername'] as String? ?? '',
-  cloudPassword: json['cloudPassword'] as String? ?? '',
-  cloudRemotePath: json['cloudRemotePath'] as String? ?? '/Music/SpotiFLAC',
-  cloudAllowInsecureHttp:
-      json['cloudAllowInsecureHttp'] as bool? ?? false,
   localLibraryEnabled: json['localLibraryEnabled'] as bool? ?? false,
   localLibraryPath: json['localLibraryPath'] as String? ?? '',
   localLibraryShowDuplicates:
@@ -90,13 +82,6 @@ Map<String, dynamic> _$AppSettingsToJson(AppSettings instance) =>
       'useAllFilesAccess': instance.useAllFilesAccess,
       'autoExportFailedDownloads': instance.autoExportFailedDownloads,
       'downloadNetworkMode': instance.downloadNetworkMode,
-      'cloudUploadEnabled': instance.cloudUploadEnabled,
-      'cloudProvider': instance.cloudProvider,
-      'cloudServerUrl': instance.cloudServerUrl,
-      'cloudUsername': instance.cloudUsername,
-      'cloudPassword': instance.cloudPassword,
-      'cloudRemotePath': instance.cloudRemotePath,
-      'cloudAllowInsecureHttp': instance.cloudAllowInsecureHttp,
       'localLibraryEnabled': instance.localLibraryEnabled,
       'localLibraryPath': instance.localLibraryPath,
       'localLibraryShowDuplicates': instance.localLibraryShowDuplicates,