feat: add sqlite-backed auth and library services

Bootstrap SQLite on server startup with embedded migrations and development seed data. Replace placeholder auth and library responses with database-backed services, bearer sessions, and repository-driven API handlers.

internal/db/migrations/0001_initial.sql

@@ -0,0 +1,87 @@
+CREATE TABLE IF NOT EXISTS users (
+  id TEXT PRIMARY KEY,
+  username TEXT NOT NULL UNIQUE,
+  password_hash TEXT NOT NULL,
+  is_admin INTEGER NOT NULL DEFAULT 0,
+  created_at TEXT NOT NULL,
+  last_login_at TEXT
+);
+
+CREATE TABLE IF NOT EXISTS sessions (
+  token TEXT PRIMARY KEY,
+  user_id TEXT NOT NULL,
+  created_at TEXT NOT NULL,
+  expires_at TEXT NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS library_roots (
+  id TEXT PRIMARY KEY,
+  path TEXT NOT NULL UNIQUE,
+  created_at TEXT NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS artists (
+  id TEXT PRIMARY KEY,
+  name TEXT NOT NULL,
+  sort_name TEXT,
+  cover_art_id TEXT,
+  created_at TEXT NOT NULL,
+  updated_at TEXT NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS albums (
+  id TEXT PRIMARY KEY,
+  artist_id TEXT NOT NULL,
+  title TEXT NOT NULL,
+  sort_title TEXT,
+  year INTEGER,
+  genre TEXT,
+  cover_art_id TEXT,
+  created_at TEXT NOT NULL,
+  updated_at TEXT NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS tracks (
+  id TEXT PRIMARY KEY,
+  album_id TEXT NOT NULL,
+  artist_id TEXT NOT NULL,
+  title TEXT NOT NULL,
+  track_number INTEGER,
+  disc_number INTEGER,
+  duration_seconds INTEGER,
+  file_path TEXT NOT NULL UNIQUE,
+  content_type TEXT,
+  created_at TEXT NOT NULL,
+  updated_at TEXT NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS playlists (
+  id TEXT PRIMARY KEY,
+  user_id TEXT NOT NULL,
+  name TEXT NOT NULL,
+  comment TEXT,
+  public INTEGER NOT NULL DEFAULT 0,
+  created_at TEXT NOT NULL,
+  updated_at TEXT NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS playlist_tracks (
+  playlist_id TEXT NOT NULL,
+  track_id TEXT NOT NULL,
+  position INTEGER NOT NULL,
+  PRIMARY KEY (playlist_id, position)
+);
+
+CREATE TABLE IF NOT EXISTS favorites (
+  user_id TEXT NOT NULL,
+  entity_id TEXT NOT NULL,
+  entity_type TEXT NOT NULL,
+  created_at TEXT NOT NULL,
+  PRIMARY KEY (user_id, entity_id, entity_type)
+);
+
+CREATE INDEX IF NOT EXISTS idx_users_username ON users(username);
+CREATE INDEX IF NOT EXISTS idx_sessions_user_id ON sessions(user_id);
+CREATE INDEX IF NOT EXISTS idx_albums_artist_id ON albums(artist_id);
+CREATE INDEX IF NOT EXISTS idx_tracks_album_id ON tracks(album_id);
+CREATE INDEX IF NOT EXISTS idx_tracks_artist_id ON tracks(artist_id);