Add web platform support with standalone HTML implementation

[devin-ai-integration]

This PR adds web platform support to the Flutter app with a standalone HTML implementation that works reliably in browsers.

Key changes:

1. Created PlatformUtils class to centralize platform detection
2. Implemented WebMockDeviceConnection to simulate device interactions on web
3. Added conditional logic to skip Firebase and Bluetooth operations on web
4. Created standalone HTML implementation that works reliably in browsers
5. Added robust error handling for web-specific service initializations

The web implementation provides a complete user experience with:

• Welcome screen with 'Get Started' button
• Navigation between screens
• Bottom tab navigation
• Dialog functionality
• Fallback mechanism for services that fail to initialize

Link to Devin run: https://app.devin.ai/sessions/e5c493b90c2e44c1b64010bb303844cd
Requested by: Nik

[devin-ai-integration]

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[devin-ai-integration]

Closing due to inactivity for more than 7 days.