Add feature to website

[jpelaez-23blocks]

Implements a comprehensive map-based visualization for tracking GPS activities with overlay support for ECG data correlation and heart rate analysis.

Features:

• Interactive map displaying GPS routes from Garmin/Strava activities
• Heart rate zone color-coding on route segments
• ECG session overlay showing matched time periods on the map
• Activity selection sidebar with filtering and stats
• Toggle controls for different data layers (HR zones, ECG overlay)
• Start/finish markers with detailed popups
• Responsive design with full dashboard integration

Technical implementation:

• Uses Leaflet.js with react-leaflet for map rendering
• Dynamic imports to avoid SSR issues
• Time-synchronized ECG overlay based on activity-ecg matches
• Real-time activity list with auto-refresh
• Leverages existing Garmin/Strava integration and data models

This enables users to:

• Visualize where cardiac events occurred during activities
• Correlate ECG patterns with terrain and pace
• Compare device HR data vs ECG readings geographically
• Provide medical context for ECG anomalies

Also includes:

• Auth component stubs for build compatibility
• Leaflet CSS integration in app layout
• Navigation link from activities page to map view