DB-first library reads, mixed library indexing, and manual NFO refresh

- API reads now serve from media_items cache instead of scanning the filesystem
  on every request; scans (manual or scheduled) remain the write path
- NFO metadata is no longer parsed automatically during scans; title falls back
  to folder/filename — metadata can be refreshed per-item via the kabob menu
- Mixed libraries are now indexed in media_items (new mixed_file item type)
  with file_path stored; scanMixed walks recursively and upserts all files
- Added file_path column to media_items and migrated item_type CHECK constraint
  to include mixed_file via safe table-recreation migration
- New POST /api/nfo-refresh endpoint reads the .nfo for a single item and
  patches its DB row (supports movie, tv_series, tv_episode)
- Added "Refresh metadata" button to movie and TV series kabob menus

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

src/lib/db.ts

@@ -81,13 +81,14 @@ function initDb(db: Database.Database): void {
       id          INTEGER PRIMARY KEY AUTOINCREMENT,
       library_id  TEXT NOT NULL REFERENCES libraries(id) ON DELETE CASCADE,
       item_key    TEXT NOT NULL UNIQUE,
-      item_type   TEXT NOT NULL CHECK(item_type IN ('movie','tv_series','tv_season','tv_episode','game','game_series')),
+      item_type   TEXT NOT NULL CHECK(item_type IN ('movie','tv_series','tv_season','tv_episode','game','game_series','mixed_file')),
       parent_key  TEXT,
       title       TEXT,
       year        INTEGER,
       plot        TEXT,
       genres      TEXT,
       metadata    TEXT,
+      file_path   TEXT,
       scanned_at  INTEGER NOT NULL
     );
 
@@ -96,6 +97,7 @@ function initDb(db: Database.Database): void {
   `)
 
   migrateLibrariesType(db)
+  migrateMediaItemsSchema(db)
   seedAppSettings(db)
 }
 
@@ -113,6 +115,53 @@ function seedAppSettings(db: Database.Database): void {
   }
 }
 
+function migrateMediaItemsSchema(db: Database.Database): void {
+  const row = db
+    .prepare("SELECT sql FROM sqlite_master WHERE type='table' AND name='media_items'")
+    .get() as { sql: string } | undefined
+
+  if (!row) return
+
+  const needsFilePath = !row.sql.includes('file_path')
+  const needsMixedFile = !row.sql.includes("'mixed_file'")
+
+  if (!needsFilePath && !needsMixedFile) return
+
+  // Determine whether the current table already has file_path (partial migration)
+  const hasFilePath = !needsFilePath ? 'file_path,' : 'NULL as file_path,'
+
+  db.exec(`
+    BEGIN TRANSACTION;
+    CREATE TABLE media_items_new (
+      id          INTEGER PRIMARY KEY AUTOINCREMENT,
+      library_id  TEXT NOT NULL REFERENCES libraries(id) ON DELETE CASCADE,
+      item_key    TEXT NOT NULL UNIQUE,
+      item_type   TEXT NOT NULL CHECK(item_type IN (
+                    'movie','tv_series','tv_season','tv_episode',
+                    'game','game_series','mixed_file')),
+      parent_key  TEXT,
+      title       TEXT,
+      year        INTEGER,
+      plot        TEXT,
+      genres      TEXT,
+      metadata    TEXT,
+      file_path   TEXT,
+      scanned_at  INTEGER NOT NULL
+    );
+    INSERT INTO media_items_new
+      SELECT id, library_id, item_key, item_type, parent_key,
+             title, year, plot, genres, metadata,
+             ${hasFilePath}
+             scanned_at
+      FROM media_items;
+    DROP TABLE media_items;
+    ALTER TABLE media_items_new RENAME TO media_items;
+    CREATE INDEX media_items_library_id ON media_items(library_id);
+    CREATE INDEX media_items_parent_key ON media_items(parent_key);
+    COMMIT;
+  `)
+}
+
 function migrateLibrariesType(db: Database.Database): void {
   const row = db
     .prepare("SELECT sql FROM sqlite_master WHERE type='table' AND name='libraries'")