Add persistence layer: TOTP auth, game history, restore

- db/ package: async SQLAlchemy engine + Player/Game/Guess models
- api/auth.py: passwordless TOTP login (pyotp), session token via socket auth
- api/history.py: record guesses/points, DB-backed standings, restore
  unfinished games on startup, host-only end_game
- api/__init__.py: auth-gated handlers, accounts map, rejoin via account
- frontend: Auth (QR + code) and History pages, resume/end-game in lobby/table
- docker-compose: real PostgreSQL service wired via DATABASE_URL
- tests_history.py for the persistence/auth layer; refresh CLAUDE.md

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/package-lock.json

@@ -8,6 +8,7 @@
       "name": "bridzik-frontend",
       "version": "0.1.0",
       "dependencies": {
+        "qrcode.react": "^4.1.0",
         "react": "^18.3.1",
         "react-dom": "^18.3.1",
         "react-router-dom": "^6.26.0",
@@ -5353,6 +5354,15 @@
         "node": ">=6"
       }
     },
+    "node_modules/qrcode.react": {
+      "version": "4.2.0",
+      "resolved": "https://registry.npmjs.org/qrcode.react/-/qrcode.react-4.2.0.tgz",
+      "integrity": "sha512-QpgqWi8rD9DsS9EP3z7BT+5lY5SFhsqGjpgW5DY/i3mK4M9DTBNz3ErMi8BWYEfI3L0d8GIbGmcdFAS1uIRGjA==",
+      "license": "ISC",
+      "peerDependencies": {
+        "react": "^16.8.0 || ^17.0.0 || ^18.0.0 || ^19.0.0"
+      }
+    },
     "node_modules/queue-microtask": {
       "version": "1.2.3",
       "resolved": "https://registry.npmjs.org/queue-microtask/-/queue-microtask-1.2.3.tgz",