Support multiple tracked people with colored markers and watch menu

- Replace single tracking with list of TrackedPerson objects in ShareProvider
- Each tracked person gets a unique color from a predefined palette
- Add watch menu (bottom sheet) with list of tracked people, coordinates, and remove buttons
- Add ability to add new tracked people by Share ID
- Render multiple colored markers on the map
- Start/stop periodic polling for all tracked people

lib/providers/share_provider.dart

@@ -1,37 +1,62 @@
+import 'dart:async';
 import 'package:flutter/material.dart';
 import '../services/share_service.dart';
 
+class TrackedPerson {
+  final String shareId;
+  final String name;
+  final Color color;
+  Map<String, dynamic>? position;
+  Timer? timer;
+
+  TrackedPerson({
+    required this.shareId,
+    required this.color,
+    this.name = '',
+    this.position,
+    this.timer,
+  });
+}
+
 class ShareProvider with ChangeNotifier {
   final ShareService _shareService;
-  
+
   String _shareId = '';
   String _geoId = '';
   bool _isLoading = false;
   String _error = '';
-  
+
   Map<String, dynamic>? _position;
-  
-  String _trackingShareId = '';
-  String _trackingToken = '';
-  Map<String, dynamic>? _trackedPosition;
-  
-  ShareProvider({ShareService? shareService}) 
-      : _shareService = shareService ?? ShareService();
-  
+
+  final List<TrackedPerson> _trackedPeople = [];
+  final List<Color> _markerColors = [
+    Colors.red,
+    Colors.green,
+    Colors.orange,
+    Colors.purple,
+    Colors.teal,
+    Colors.pink,
+    Colors.brown,
+    Colors.indigo,
+  ];
+  int _nextColorIndex = 0;
+
+  ShareProvider({ShareService? shareService})
+    : _shareService = shareService ?? ShareService();
+
   String get shareId => _shareId;
   String get geoId => _geoId;
   bool get isLoading => _isLoading;
   String get error => _error;
   Map<String, dynamic>? get position => _position;
-  
-  String get trackingShareId => _trackingShareId;
-  Map<String, dynamic>? get trackedPosition => _trackedPosition;
-  
+
+  List<TrackedPerson> get trackedPeople => List.unmodifiable(_trackedPeople);
+
   Future<void> createShare(String token, double x, double y) async {
     _isLoading = true;
     _error = '';
     notifyListeners();
-    
+
     try {
       final result = await _shareService.createShare(token, x, y);
       _geoId = result['geo_id']?.toString() ?? '';
@@ -46,12 +71,12 @@ class ShareProvider with ChangeNotifier {
       notifyListeners();
     }
   }
-  
+
   Future<void> getPosition(String token, String shareId) async {
     _isLoading = true;
     _error = '';
     notifyListeners();
-    
+
     try {
       _position = await _shareService.getPositionByShareId(token, shareId);
       notifyListeners();
@@ -64,7 +89,7 @@ class ShareProvider with ChangeNotifier {
       notifyListeners();
     }
   }
-  
+
   void clearShare() {
     _shareId = '';
     _geoId = '';
@@ -72,20 +97,29 @@ class ShareProvider with ChangeNotifier {
     notifyListeners();
   }
 
-  Future<void> startTracking(String shareId, String token) async {
-    _trackingShareId = shareId;
-    _trackingToken = token;
-    _error = '';
+  Future<void> addTracking(String shareId, String token) async {
+    if (_trackedPeople.any((p) => p.shareId == shareId)) return;
+
+    final color = _markerColors[_nextColorIndex % _markerColors.length];
+    _nextColorIndex++;
+
+    final person = TrackedPerson(
+      shareId: shareId,
+      color: color,
+      name: 'Person ${_trackedPeople.length + 1}',
+    );
+    _trackedPeople.add(person);
     notifyListeners();
-    
-    await updateTrackedPosition();
+
+    await _updatePersonPosition(token, person);
   }
 
-  Future<void> updateTrackedPosition() async {
-    if (_trackingShareId.isEmpty) return;
-    
+  Future<void> _updatePersonPosition(String token, TrackedPerson person) async {
     try {
-      _trackedPosition = await _shareService.getPositionByShareId(_trackingToken, _trackingShareId);
+      person.position = await _shareService.getPositionByShareId(
+        token,
+        person.shareId,
+      );
       notifyListeners();
     } catch (e) {
       _error = e.toString();
@@ -93,10 +127,30 @@ class ShareProvider with ChangeNotifier {
     }
   }
 
-  void stopTracking() {
-    _trackingShareId = '';
-    _trackingToken = '';
-    _trackedPosition = null;
+  void startTrackingPolling(String token) {
+    for (final person in _trackedPeople) {
+      person.timer = Timer.periodic(
+        const Duration(seconds: 5),
+        (_) => _updatePersonPosition(token, person),
+      );
+    }
+  }
+
+  void removeTracking(String shareId) {
+    final index = _trackedPeople.indexWhere((p) => p.shareId == shareId);
+    if (index != -1) {
+      _trackedPeople[index].timer?.cancel();
+      _trackedPeople.removeAt(index);
+      notifyListeners();
+    }
+  }
+
+  void stopAllTracking() {
+    for (final person in _trackedPeople) {
+      person.timer?.cancel();
+    }
+    _trackedPeople.clear();
+    _nextColorIndex = 0;
     notifyListeners();
   }
-}
+}