Add Phase 1 MVP: D&D text-adventure server

FastAPI + Postgres backend with fastapi-users auth, games/characters
CRUD, and a WebSocket chat endpoint where an x.ai Grok DM narrates
play, rolls dice, and maintains character sheets via tool calls.
React + Tailwind frontend covers registration/login, game list and
creation, participation-code join flow, character viewer, and a
real-time chat session view. Docker Compose skeleton (Postgres +
backend) included; Caddy/frontend container wiring is deferred to
the deploy milestone.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/app/auth/users.py

@@ -0,0 +1,68 @@
+import uuid
+from collections.abc import AsyncGenerator
+
+from fastapi import Depends, Request
+from fastapi_users import BaseUserManager, FastAPIUsers, UUIDIDMixin
+from fastapi_users.authentication import (
+    AuthenticationBackend,
+    BearerTransport,
+    JWTStrategy,
+)
+from fastapi_users.db import SQLAlchemyUserDatabase
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.auth.email import send_email
+from app.config import settings
+from app.db import get_async_session
+from app.models.user import User
+
+JWT_LIFETIME_SECONDS = 60 * 60 * 24 * 7  # 7 days
+
+
+async def get_user_db(
+    session: AsyncSession = Depends(get_async_session),
+) -> AsyncGenerator[SQLAlchemyUserDatabase, None]:
+    yield SQLAlchemyUserDatabase(session, User)
+
+
+class UserManager(UUIDIDMixin, BaseUserManager[User, uuid.UUID]):
+    reset_password_token_secret = settings.reset_password_secret
+    verification_token_secret = settings.verification_token_secret
+
+    async def on_after_forgot_password(
+        self, user: User, token: str, request: Request | None = None
+    ) -> None:
+        reset_url = f"{settings.frontend_origin}/reset-password?token={token}"
+        await send_email(
+            to=user.email,
+            subject="Passwort zurücksetzen — DungeonsDragons",
+            body=(
+                f"Hallo {user.name},\n\n"
+                f"klicke auf den folgenden Link, um dein Passwort zurückzusetzen:\n{reset_url}\n\n"
+                "Falls du das nicht angefordert hast, ignoriere diese E-Mail."
+            ),
+        )
+
+
+async def get_user_manager(
+    user_db: SQLAlchemyUserDatabase = Depends(get_user_db),
+) -> AsyncGenerator[UserManager, None]:
+    yield UserManager(user_db)
+
+
+bearer_transport = BearerTransport(tokenUrl="auth/jwt/login")
+
+
+def get_jwt_strategy() -> JWTStrategy:
+    return JWTStrategy(secret=settings.jwt_secret, lifetime_seconds=JWT_LIFETIME_SECONDS)
+
+
+auth_backend = AuthenticationBackend(
+    name="jwt",
+    transport=bearer_transport,
+    get_strategy=get_jwt_strategy,
+)
+
+fastapi_users = FastAPIUsers[User, uuid.UUID](get_user_manager, [auth_backend])
+
+current_active_user = fastapi_users.current_user(active=True)