feat(catalog): persist bounds filter state in URL

- Add urlBounds and filterByBounds computed from URL query
- Add setBoundsInUrl and clearBoundsFromUrl actions
- Update index.vue to use URL-based bounds state
- Bounds written to URL as comma-separated values (west,south,east,north)

This enables sharing links with map viewport bounds filter.

app/pages/catalog/index.vue

@@ -13,7 +13,7 @@
     :related-points="relatedPoints"
     @select="onMapSelect"
     @bounds-change="onBoundsChange"
-    @update:filter-by-bounds="filterByBounds = $event"
+    @update:filter-by-bounds="$event ? setBoundsInUrl(currentMapBounds) : clearBoundsFromUrl()"
   >
     <!-- Panel slot - shows selection list OR info OR quote results -->
     <template #panel>
@@ -82,8 +82,7 @@ const localePath = useLocalePath()
 // Ref to CatalogPage for accessing bounds
 const catalogPageRef = ref<{ currentBounds: Ref<MapBounds | null> } | null>(null)
 
-// Filter by map bounds state
-const filterByBounds = ref(false)
+// Current map bounds (local state, updated when map moves)
 const currentMapBounds = ref<MapBounds | null>(null)
 
 // Hovered item for map highlight
@@ -103,6 +102,10 @@ const currentSelectionItems = computed(() => {
 // Handle bounds change from map
 const onBoundsChange = (bounds: MapBounds) => {
   currentMapBounds.value = bounds
+  // If filter by bounds is enabled, write to URL
+  if (filterByBounds.value) {
+    setBoundsInUrl(bounds)
+  }
 }
 
 const {
@@ -122,7 +125,11 @@ const {
   openInfo,
   closeInfo,
   setInfoProduct,
-  setLabel
+  setLabel,
+  urlBounds,
+  filterByBounds,
+  setBoundsInUrl,
+  clearBoundsFromUrl
 } = useCatalogSearch()
 
 // Info panel composable
@@ -230,12 +237,15 @@ watch(productId, (newProductId) => {
 }, { immediate: true })
 
 // Apply bounds filter when "filter by map bounds" is enabled
-watch([filterByBounds, currentMapBounds], ([enabled, bounds]) => {
+// Use URL bounds if available, otherwise use current map bounds
+watch([filterByBounds, urlBounds, currentMapBounds], ([enabled, urlB, mapB]) => {
+  // Use URL bounds if available, otherwise current map bounds
+  const bounds = urlB || mapB
   const boundsToApply = enabled && bounds ? bounds : null
   setHubBoundsFilter(boundsToApply)
   setSupplierBoundsFilter(boundsToApply)
   setProductBoundsFilter(boundsToApply)
-})
+}, { immediate: true })
 
 // Watch infoId to load info data
 watch(infoId, async (info) => {