feat: video support + Memories music choices

Videos:
- Worker ingests .mp4 .mov .m4v .avi .mkv .webm .3gp via ffmpeg/ffprobe
  (frame extract → sharp resize, same thumbnail pipeline as photos)
- DB: media_type + duration columns with migration
- GET /api/videos returns all indexed videos
- GET /api/photos/:id/video streams original file with Range support
  for browser seek/scrub
- VideosView: 16:9 thumbnail grid, play-button overlay, duration badge
- Full-screen player: native <video controls>, ESC to close
- Library tab now excludes videos (dedicated Videos tab)
- Dockerfile: adds ffmpeg to runtime stage

Memories music choices:
- Three styles: ⚡ Upbeat (G-major, default), 🌙 Dreamy (A-minor),
  🎬 Cinematic (D-minor, dual-oscillator richness)
- Shared Web Audio engine (reverb, LPF, pad + melody)
- Style picker in header; active style icon shown in slideshow bar

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

worker/db.js

@@ -113,8 +113,11 @@ export function openDb(dbPath) {
   try { db.exec('ALTER TABLE photos ADD COLUMN starred INTEGER NOT NULL DEFAULT 0'); } catch {}
   try { db.exec('ALTER TABLE photos ADD COLUMN place_city    TEXT'); } catch {}
   try { db.exec('ALTER TABLE photos ADD COLUMN place_country TEXT'); } catch {}
-  db.exec('CREATE INDEX IF NOT EXISTS idx_photos_starred    ON photos(starred)');
-  db.exec('CREATE INDEX IF NOT EXISTS idx_photos_place_city ON photos(place_city)');
+  try { db.exec("ALTER TABLE photos ADD COLUMN media_type TEXT NOT NULL DEFAULT 'photo'"); } catch {}
+  try { db.exec('ALTER TABLE photos ADD COLUMN duration REAL'); } catch {}
+  db.exec('CREATE INDEX IF NOT EXISTS idx_photos_starred     ON photos(starred)');
+  db.exec('CREATE INDEX IF NOT EXISTS idx_photos_place_city  ON photos(place_city)');
+  db.exec('CREATE INDEX IF NOT EXISTS idx_photos_media_type  ON photos(media_type)');
 
   // Seed default settings
   const seedSetting = db.prepare('INSERT OR IGNORE INTO settings (key, value) VALUES (?, ?)');
@@ -125,11 +128,11 @@ export function openDb(dbPath) {
       INSERT OR IGNORE INTO photos
         (filepath, thumb_path, preview_path, date_taken, date_imported,
          camera_model, gps_lat, gps_lon, phash, width, height, filesize,
-         place_city, place_country)
+         place_city, place_country, media_type, duration)
       VALUES
         (@filepath, @thumb_path, @preview_path, @date_taken, @date_imported,
          @camera_model, @gps_lat, @gps_lon, @phash, @width, @height, @filesize,
-         @place_city, @place_country)
+         @place_city, @place_country, @media_type, @duration)
     `),
     exists:   db.prepare('SELECT 1 FROM photos WHERE filepath = ? LIMIT 1'),
     remove:   db.prepare('DELETE FROM photos WHERE filepath = ?'),