feat(import): selective GPX/KML element import and performance improvements

Add type-selector UI in the file import modal letting users choose which
GPX elements (waypoints, routes, tracks) or KML/KMZ elements (points,
paths) to import. KML LineString placemarks are now imported as path
places with route_geometry.

Performance improvements:
- Extract MemoPlaceRow with React.memo and contentVisibility:auto to cut
  unnecessary re-renders in PlacesSidebar
- Add weatherQueue to cap concurrent weather fetches at 3
- Replace sequential per-place deletes with a single bulkDelete API call
  (new DELETE /places/bulk endpoint + deletePlacesMany service)
- Memoize atlas/photo/weather service calls to avoid redundant requests
- Add multi-select mode to PlacesSidebar for bulk operations

Add large GPX/KML/KMZ fixtures for integration/perf testing and two
profiler analysis scripts under scripts/.

client/src/services/photoService.ts

@@ -12,6 +12,29 @@ const listeners = new Map<string, Set<(entry: PhotoEntry) => void>>()
 // Separate thumb listeners — called when thumbDataUrl becomes available after initial load
 const thumbListeners = new Map<string, Set<(thumb: string) => void>>()
 
+// Concurrency limiter — at most N photo API requests in flight at once.
+// Prevents flooding the server (and external APIs it calls) when many places appear at once.
+const MAX_CONCURRENT = 5
+let activeRequests = 0
+const requestQueue: Array<() => void> = []
+
+function acquireRequestSlot(): Promise<void> {
+  if (activeRequests < MAX_CONCURRENT) {
+    activeRequests++
+    return Promise.resolve()
+  }
+  return new Promise(resolve => requestQueue.push(resolve))
+}
+
+function releaseRequestSlot(): void {
+  const next = requestQueue.shift()
+  if (next) {
+    next()
+  } else {
+    activeRequests--
+  }
+}
+
 function notify(key: string, entry: PhotoEntry) {
   listeners.get(key)?.forEach(fn => fn(entry))
   listeners.delete(key)
@@ -99,37 +122,39 @@ export function fetchPhoto(
   }
 
   inFlight.add(cacheKey)
-  mapsApi.placePhoto(photoId, lat, lng, name)
-    .then(async (data: { photoUrl?: string }) => {
-      const photoUrl = data.photoUrl || null
-      if (!photoUrl) {
+  acquireRequestSlot().then(() =>
+    mapsApi.placePhoto(photoId, lat, lng, name)
+      .then(async (data: { photoUrl?: string }) => {
+        const photoUrl = data.photoUrl || null
+        if (!photoUrl) {
+          const entry: PhotoEntry = { photoUrl: null, thumbDataUrl: null }
+          cache.set(cacheKey, entry)
+          callback?.(entry)
+          notify(cacheKey, entry)
+          return
+        }
+
+        // Store URL first — sidebar can show immediately
+        const entry: PhotoEntry = { photoUrl, thumbDataUrl: null }
+        cache.set(cacheKey, entry)
+        callback?.(entry)
+        notify(cacheKey, entry)
+
+        // Generate base64 thumb in background
+        const thumb = await urlToBase64(photoUrl)
+        if (thumb) {
+          entry.thumbDataUrl = thumb
+          notifyThumb(cacheKey, thumb)
+        }
+      })
+      .catch(() => {
         const entry: PhotoEntry = { photoUrl: null, thumbDataUrl: null }
         cache.set(cacheKey, entry)
         callback?.(entry)
         notify(cacheKey, entry)
-        return
-      }
-
-      // Store URL first — sidebar can show immediately
-      const entry: PhotoEntry = { photoUrl, thumbDataUrl: null }
-      cache.set(cacheKey, entry)
-      callback?.(entry)
-      notify(cacheKey, entry)
-
-      // Generate base64 thumb in background
-      const thumb = await urlToBase64(photoUrl)
-      if (thumb) {
-        entry.thumbDataUrl = thumb
-        notifyThumb(cacheKey, thumb)
-      }
-    })
-    .catch(() => {
-      const entry: PhotoEntry = { photoUrl: null, thumbDataUrl: null }
-      cache.set(cacheKey, entry)
-      callback?.(entry)
-      notify(cacheKey, entry)
-    })
-    .finally(() => { inFlight.delete(cacheKey) })
+      })
+      .finally(() => { inFlight.delete(cacheKey); releaseRequestSlot() })
+  )
 }
 
 export function getAllThumbs(): Record<string, string> {