feat: Persist location sharing across browser sessions

- Remember location sharing preference per room
- Auto-start sharing when returning to a room
- Restore last known location immediately on page load (if < 1 hour old)
- Location updates are saved to localStorage for faster reload

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/app/[slug]/page.tsx

@@ -31,8 +31,9 @@ export default function RoomPage() {
   const [showMeetingPoint, setShowMeetingPoint] = useState(false);
   const [currentUser, setCurrentUser] = useState<{ name: string; emoji: string } | null>(null);
   const [selectedParticipant, setSelectedParticipant] = useState<Participant | null>(null);
+  const [shouldAutoStartSharing, setShouldAutoStartSharing] = useState(false);
 
-  // Load user from localStorage
+  // Load user and sharing preference from localStorage
   useEffect(() => {
     const stored = localStorage.getItem('rmaps_user');
     if (stored) {
@@ -40,8 +41,15 @@ export default function RoomPage() {
     } else {
       // Redirect to home if no user info
       router.push('/');
+      return;
     }
-  }, [router]);
+
+    // Check if user had location sharing enabled for this room
+    const sharingPref = localStorage.getItem(`rmaps_sharing_${slug}`);
+    if (sharingPref === 'true') {
+      setShouldAutoStartSharing(true);
+    }
+  }, [router, slug]);
 
   // Room hook (only initialize when we have user info)
   const {
@@ -77,13 +85,24 @@ export default function RoomPage() {
     updateLocationRef.current = updateLocation;
   }, [updateLocation]);
 
-  // Stable callback that always uses latest refs
+  // Stable callback that always uses latest refs - also persists location
   const handleLocationUpdate = useCallback((location: ParticipantLocation) => {
     console.log('Location update received:', location.latitude, location.longitude, 'connected:', isConnectedRef.current);
     if (isConnectedRef.current) {
       updateLocationRef.current(location);
+      // Persist last known location for faster reload
+      try {
+        localStorage.setItem(`rmaps_last_location_${slug}`, JSON.stringify({
+          latitude: location.latitude,
+          longitude: location.longitude,
+          accuracy: location.accuracy,
+          timestamp: location.timestamp.toISOString(),
+        }));
+      } catch {
+        // Ignore storage errors
+      }
     }
-  }, []);
+  }, [slug]);
 
   // Location sharing hook
   const {
@@ -97,18 +116,58 @@ export default function RoomPage() {
     highAccuracy: true,
   });
 
-  // Location sharing is opt-in - user must click to start
-  // Handler for toggling location sharing
+  // Restore last known location immediately when connected
+  const hasRestoredLocationRef = useRef(false);
+  useEffect(() => {
+    if (isConnected && !hasRestoredLocationRef.current) {
+      hasRestoredLocationRef.current = true;
+      try {
+        const savedLocation = localStorage.getItem(`rmaps_last_location_${slug}`);
+        if (savedLocation) {
+          const loc = JSON.parse(savedLocation);
+          // Only restore if less than 1 hour old
+          const age = Date.now() - new Date(loc.timestamp).getTime();
+          if (age < 60 * 60 * 1000) {
+            console.log('Restoring last known location:', loc.latitude, loc.longitude);
+            updateLocation({
+              latitude: loc.latitude,
+              longitude: loc.longitude,
+              accuracy: loc.accuracy || 100,
+              timestamp: new Date(loc.timestamp),
+              source: 'gps',
+            });
+          }
+        }
+      } catch {
+        // Ignore restore errors
+      }
+    }
+  }, [isConnected, slug, updateLocation]);
+
+  // Auto-start location sharing if user had it enabled before
+  useEffect(() => {
+    if (shouldAutoStartSharing && isConnected && !isSharing) {
+      console.log('Auto-starting location sharing from saved preference');
+      startSharing();
+      setShouldAutoStartSharing(false); // Only auto-start once
+    }
+  }, [shouldAutoStartSharing, isConnected, isSharing, startSharing]);
+
+  // Handler for toggling location sharing - persists preference
   const handleToggleSharing = useCallback(() => {
     if (isSharing) {
       console.log('Stopping location sharing and clearing location');
       stopSharing();
       clearLocation();
+      // Save preference
+      localStorage.setItem(`rmaps_sharing_${slug}`, 'false');
     } else {
       console.log('Starting location sharing');
       startSharing();
+      // Save preference
+      localStorage.setItem(`rmaps_sharing_${slug}`, 'true');
     }
-  }, [isSharing, startSharing, stopSharing, clearLocation]);
+  }, [isSharing, startSharing, stopSharing, clearLocation, slug]);
 
   // Track if we've centered on user's location yet
   const hasCenteredRef = useRef(false);