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/composables/useCatalogSearch.ts

@@ -84,6 +84,18 @@ export function useCatalogSearch() {
   const hubId = computed(() => route.query.hub as string | undefined)
   const quantity = computed(() => route.query.qty as string | undefined)
 
+  // Map bounds from URL (format: west,south,east,north)
+  const urlBounds = computed(() => {
+    const b = route.query.bounds as string | undefined
+    if (!b) return null
+    const parts = b.split(',').map(Number)
+    if (parts.length !== 4 || parts.some(isNaN)) return null
+    return { west: parts[0], south: parts[1], east: parts[2], north: parts[3] }
+  })
+
+  // Filter by bounds checkbox state from URL
+  const filterByBounds = computed(() => route.query.bounds !== undefined)
+
   // Get label for a filter (from cache or fallback to ID)
   const getLabel = (type: string, id: string | undefined): string | null => {
     if (!id) return null
@@ -237,6 +249,21 @@ export function useCatalogSearch() {
     updateQuery({ qty })
   }
 
+  // Set map bounds in URL (for filter by map feature)
+  const setBoundsInUrl = (bounds: { west: number; south: number; east: number; north: number } | null) => {
+    if (bounds) {
+      const boundsStr = `${bounds.west.toFixed(4)},${bounds.south.toFixed(4)},${bounds.east.toFixed(4)},${bounds.north.toFixed(4)}`
+      updateQuery({ bounds: boundsStr })
+    } else {
+      updateQuery({ bounds: null })
+    }
+  }
+
+  // Clear bounds from URL
+  const clearBoundsFromUrl = () => {
+    updateQuery({ bounds: null })
+  }
+
   const openInfo = (type: InfoEntityType, uuid: string) => {
     updateQuery({ info: `${type}:${uuid}`, select: null, infoTab: null, infoProduct: null })
   }
@@ -350,6 +377,8 @@ export function useCatalogSearch() {
     quantity,
     searchQuery,
     mapViewMode,
+    urlBounds,
+    filterByBounds,
 
     // Drawer state
     isDrawerOpen,
@@ -373,6 +402,8 @@ export function useCatalogSearch() {
     removeFilter,
     editFilter,
     setQuantity,
+    setBoundsInUrl,
+    clearBoundsFromUrl,
     openInfo,
     closeInfo,
     setInfoTab,