feat: v0.4 — satellite imagery, KiwiSDR radio, LOCATE bar & security cleanup

New features:
- NASA GIBS (MODIS Terra) daily satellite imagery with 30-day time slider
- Esri World Imagery high-res satellite layer (sub-meter, zoom 18+)
- KiwiSDR SDR receivers on map with embedded radio tuner
- Sentinel-2 intel card — right-click for recent satellite photo popup
- LOCATE bar — search by coordinates or place name (Nominatim geocoding)
- SATELLITE style preset in bottom bar cycling
- v0.4 changelog modal on first launch

Fixes:
- Satellite imagery renders below data icons (imagery-ceiling anchor)
- Sentinel-2 opens full-res PNG directly (not STAC catalog JSON)
- Light/dark theme: UI stays dark, only map basemap changes

Security:
- Removed test files with hardcoded API keys from tracking
- Removed .git_backup directory from tracking
- Updated .gitignore to exclude test files, dev scripts, cache files

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

.gitignore

@@ -70,3 +70,21 @@ backend/dump.json
 backend/debug_fast.json
 *.zip
 .git_backup/
+
+# Test files (may contain hardcoded keys)
+backend/test_*.py
+backend/services/test_*.py
+
+# Local analysis & dev tools
+backend/analyze_xlsx.py
+backend/xlsx_analysis.txt
+backend/services/ais_cache.json
+
+# Internal update tracking (not for repo)
+updatestuff.md
+
+# Misc dev artifacts
+clean_zip.py
+zip_repo.py
+refactor_cesium.py
+jobs.json