v2.1.0: Add floating window overlay functionality

Major Features:
- Floating overlay window with system-level persistence
- Split decimal display (main speed prominent, decimal smaller/faded)
- Optimized content sizing for maximum readability
- Navigation icon trigger for overlay activation
- Multiple close options (overlay button + long-press navigation)

Technical Implementation:
- Added flutter_overlay_window dependency
- Android SYSTEM_ALERT_WINDOW permissions
- Overlay service configuration in AndroidManifest
- Enhanced flex ratios for better space utilization
- BoxFit.contain for improved content scaling

UX Improvements:
- Streamlined overlay launch (removed permission prompts)
- Cleaner visual hierarchy with split speed display
- Responsive design for both portrait and landscape
- Professional overlay styling matching app theme

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

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

CLAUDE.md

@@ -3,8 +3,8 @@
 ## Project Overview
 A customizable Flutter GPS speedometer app targeting Android devices, emphasizing modularity and user customization.
 
-## Current Status: v1.1 Complete 
-**Enhanced GPS speedometer with improved user experience and customization options.**
+## Current Status: v2.1.0 Complete 
+**GPS speedometer with floating window overlay functionality and optimized visual design.**
 
 ### Architecture Implemented
 - **State Management:** Provider pattern
@@ -31,10 +31,18 @@ Architecture: Provider + Consumer pattern for reactive state management
 Permissions: Location services with graceful degradation
 ```
 
-## Recent Updates (v1.1)
+## Recent Updates (v2.1.0)
 
 ### ✅ Completed Features
-- [x] **Portrait/Landscape Support**: Automatic orientation detection implemented
+- [x] **Floating Window Overlay**: System-level overlay window for persistent speed display
+- [x] **Split Decimal Display**: Main speed prominent, decimal fraction smaller and faded
+- [x] **Optimized Content Sizing**: Maximized readability with improved flex ratios
+- [x] **Navigation Icon Trigger**: Tap compass area to launch floating window
+- [x] **Multiple Close Options**: Overlay close button and long-press navigation area
+- [x] **Android Permissions**: SYSTEM_ALERT_WINDOW and foreground service support
+
+### Previous Updates (v1.1)
+- [x] **Portrait/Landscape Support**: Automatic orientation detection implemented  
 - [x] **Interactive Gauge**: Click gauge face to switch digital/analog modes
 - [x] **Extended Speed Units**: Added knots support with quick selector buttons