feat: places (reverse geocoding) + folder browser

Places:
- worker/geocode.js: Nominatim reverse geocoder, 1 req/sec rate limit,
  in-memory cache keyed to 3-decimal-place coordinates
- Ingest calls reverseGeocode() for any photo with GPS data; stores
  place_city and place_country on the photo row
- DB migrations add place_city / place_country columns + index on place_city
- Stats API returns cities grouped by count
- buildFilter() supports ?city= parameter
- FilterSidebar shows a Places section with city list + country sublabel

Folder browser:
- GET /api/fs/browse?path=… lists subdirectories (path-normalized to prevent traversal)
- Settings panel: 📁 button opens inline directory browser below the add
  input — navigate with up arrow / directory clicks, Select fills the input

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

worker/ingest.js

@@ -4,6 +4,7 @@ import crypto from 'crypto';
 import sharp from 'sharp';
 import exifr from 'exifr';
 import { computeDHash } from './hash.js';
+import { reverseGeocode } from './geocode.js';
 
 const SUPPORTED = new Set([
   '.jpg', '.jpeg', '.png', '.webp', '.heic', '.heif',
@@ -37,6 +38,13 @@ export async function ingestFile(filepath, db, posterDir, settings = {}) {
   const gpsLat      = exif.latitude  ?? null;
   const gpsLon      = exif.longitude ?? null;
 
+  let placeCity = null, placeCountry = null;
+  if (gpsLat !== null && gpsLon !== null) {
+    const place = await reverseGeocode(gpsLat, gpsLon);
+    placeCity    = place?.city    ?? null;
+    placeCountry = place?.country ?? null;
+  }
+
   const { dir, thumb, preview } = posterPaths(filepath, posterDir, dateTaken ?? stat.mtime);
   fs.mkdirSync(dir, { recursive: true });
 
@@ -78,7 +86,9 @@ export async function ingestFile(filepath, db, posterDir, settings = {}) {
     phash,
     width,
     height,
-    filesize: stat.size,
+    filesize:      stat.size,
+    place_city:    placeCity,
+    place_country: placeCountry,
   });
 
   console.log(`[ingest] ${path.basename(filepath)}`);