Only fit map bounds on initial load, not on every activity update

Prevents the map from resetting zoom/pan when new activities stream
in from relays. Users can now freely zoom and pan without being
snapped back to the world view.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/modules/activities/components/ActivityMap.vue

@@ -15,6 +15,7 @@ const router = useRouter()
 const mapContainer = ref<HTMLElement | null>(null)
 let map: L.Map | null = null
 let markerGroup: L.LayerGroup | null = null
+let hasFittedBounds = false
 
 // Fix Leaflet default icon paths (broken by bundlers)
 const defaultIcon = L.icon({
@@ -90,8 +91,9 @@ function updateMarkers() {
     markerGroup.addLayer(marker)
   }
 
-  // Fit bounds if there are markers
-  if (geoActivities.length > 0) {
+  // Fit bounds only on first load, not when new activities stream in
+  if (!hasFittedBounds && geoActivities.length > 0) {
+    hasFittedBounds = true
     const bounds = L.latLngBounds(
       geoActivities.map(a => [a.coordinates!.lat, a.coordinates!.lng] as L.LatLngTuple)
     )