feat(gps-converter): add GPS coordinate converter tool

[vgpastor]

Summary

• New GPS Convertidor tool in new Utilidades category
• Geolocates user and displays coordinates in 5 formats: DD, DM, DMS, UTM, MGRS
• Reverse geocoding shows postal address
• Technical GPS details: altitude, accuracy (horizontal/vertical), speed, heading, timestamp, mock detection
• Bidirectional converter: paste coordinates in any format (DD, DM, DMS, UTM, MGRS) and convert to all others
• Navigate button opens device map app via geo: URI
• Copy to clipboard for each format
• 31 new unit tests covering all conversions and parsing

Dependencies

• geolocator: ^13.0.2 — device geolocation
• geocoding: ^3.0.0 — reverse geocoding

Permissions

• Android: ACCESS_FINE_LOCATION, ACCESS_COARSE_LOCATION
• iOS: NSLocationWhenInUseUsageDescription

Files changed

• 4 new feature files in lib/features/gps_converter/
• 1 new test file with 31 tests
• Modified: tool_category, app_colors, tool_registry, home_screen, app_router, pubspec.yaml, AndroidManifest.xml, Info.plist
• Version bump: 0.1.8 → 0.1.9

Test plan

• dart format . — 0 changes
• flutter analyze — 0 issues
• flutter test — 161 tests passed (31 new)
• Manual test on Android emulator: geolocation, conversion, copy, navigation

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