Implement complete GPS speedometer functionality

Features implemented:
- Real-time GPS speed tracking with permission handling
- Customizable speed units (km/h, mph) with persistent settings
- Digital and analog speedometer display styles
- Dark/light theme support with system integration
- Optional metrics: coordinates, distance, trip time, GPS accuracy
- Trip reset functionality and error handling
- Modular architecture with Provider state management

Technical details:
- Added dependencies: geolocator, permission_handler, provider, shared_preferences
- Configured Android location permissions (FINE_LOCATION, COARSE_LOCATION)
- Portrait orientation lock for mobile-first experience
- Extensible settings system for future customization options
- Clean separation of concerns: providers, screens, widgets

🤖 Generated with [Claude Code](https://claude.ai/code)

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

macos/Flutter/GeneratedPluginRegistrant.swift

@@ -5,6 +5,10 @@
 import FlutterMacOS
 import Foundation
 
+import geolocator_apple
+import shared_preferences_foundation
 
 func RegisterGeneratedPlugins(registry: FlutterPluginRegistry) {
+  GeolocatorPlugin.register(with: registry.registrar(forPlugin: "GeolocatorPlugin"))
+  SharedPreferencesPlugin.register(with: registry.registrar(forPlugin: "SharedPreferencesPlugin"))
 }