feat: auth-aware UI and role-based access control (#67)

## Summary

- Add `is_admin` column to users table with Alembic migration and a `require_admin` FastAPI dependency that protects all admin-facing write endpoints (games, pokemon, evolutions, bosses, routes CRUD)
- Expose admin status to frontend via user API and update AuthContext to fetch/store `isAdmin` after login
- Make navigation menu auth-aware (different links for logged-out, logged-in, and admin users) and protect frontend routes with `ProtectedRoute` and `AdminRoute` components, preserving deep-linking through redirects
- Fix test reliability: `drop_all` before `create_all` to clear stale PostgreSQL enums from interrupted test runs
- Fix test auth: add `admin_client` fixture and use valid UUID for mock user so tests pass with new admin-protected endpoints

## Test plan

- [x] All 252 backend tests pass
- [ ] Verify non-admin users cannot access admin write endpoints (games, pokemon, evolutions, bosses CRUD)
- [ ] Verify admin users can access admin endpoints normally
- [ ] Verify navigation shows correct links for logged-out, logged-in, and admin states
- [ ] Verify `/admin/*` routes redirect non-admin users with a toast
- [ ] Verify `/runs/new` and `/genlockes/new` redirect unauthenticated users to login, then back after auth

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Reviewed-on: #67
Co-authored-by: Julian Tabel <juliantabel.jt@gmail.com>
Co-committed-by: Julian Tabel <juliantabel.jt@gmail.com>

backend/tests/test_auth.py

@@ -1,12 +1,14 @@
 import time
+from uuid import UUID
 
 import jwt
 import pytest
 from httpx import ASGITransport, AsyncClient
 
-from app.core.auth import AuthUser, get_current_user, require_auth
+from app.core.auth import AuthUser, get_current_user, require_admin, require_auth
 from app.core.config import settings
 from app.main import app
+from app.models.user import User
 
 
 @pytest.fixture
@@ -177,3 +179,140 @@ async def test_read_endpoint_without_token(db_session):
     ) as ac:
         response = await ac.get("/runs")
     assert response.status_code == 200
+
+
+async def test_require_admin_valid_admin_user(db_session):
+    """Test require_admin passes through for admin user."""
+    user_id = "11111111-1111-1111-1111-111111111111"
+    admin_user = User(
+        id=UUID(user_id),
+        email="admin@example.com",
+        is_admin=True,
+    )
+    db_session.add(admin_user)
+    await db_session.commit()
+
+    auth_user = AuthUser(id=user_id, email="admin@example.com")
+    result = await require_admin(user=auth_user, session=db_session)
+    assert result is auth_user
+
+
+async def test_require_admin_non_admin_user(db_session):
+    """Test require_admin raises 403 for non-admin user."""
+    from fastapi import HTTPException
+
+    user_id = "22222222-2222-2222-2222-222222222222"
+    regular_user = User(
+        id=UUID(user_id),
+        email="user@example.com",
+        is_admin=False,
+    )
+    db_session.add(regular_user)
+    await db_session.commit()
+
+    auth_user = AuthUser(id=user_id, email="user@example.com")
+    with pytest.raises(HTTPException) as exc_info:
+        await require_admin(user=auth_user, session=db_session)
+    assert exc_info.value.status_code == 403
+    assert exc_info.value.detail == "Admin access required"
+
+
+async def test_require_admin_user_not_in_db(db_session):
+    """Test require_admin raises 403 for user not in database."""
+    from fastapi import HTTPException
+
+    auth_user = AuthUser(
+        id="33333333-3333-3333-3333-333333333333", email="ghost@example.com"
+    )
+    with pytest.raises(HTTPException) as exc_info:
+        await require_admin(user=auth_user, session=db_session)
+    assert exc_info.value.status_code == 403
+    assert exc_info.value.detail == "Admin access required"
+
+
+async def test_admin_endpoint_returns_403_for_non_admin(
+    db_session, jwt_secret, monkeypatch
+):
+    """Test that admin endpoint returns 403 for authenticated non-admin user."""
+    user_id = "44444444-4444-4444-4444-444444444444"
+    regular_user = User(
+        id=UUID(user_id),
+        email="nonadmin@example.com",
+        is_admin=False,
+    )
+    db_session.add(regular_user)
+    await db_session.commit()
+
+    monkeypatch.setattr(settings, "supabase_jwt_secret", jwt_secret)
+    token = jwt.encode(
+        {
+            "sub": user_id,
+            "email": "nonadmin@example.com",
+            "role": "authenticated",
+            "aud": "authenticated",
+            "exp": int(time.time()) + 3600,
+        },
+        jwt_secret,
+        algorithm="HS256",
+    )
+
+    async with AsyncClient(
+        transport=ASGITransport(app=app),
+        base_url="http://test",
+        headers={"Authorization": f"Bearer {token}"},
+    ) as ac:
+        response = await ac.post(
+            "/games",
+            json={
+                "name": "Test Game",
+                "slug": "test-game",
+                "generation": 1,
+                "region": "Kanto",
+                "category": "core",
+            },
+        )
+    assert response.status_code == 403
+    assert response.json()["detail"] == "Admin access required"
+
+
+async def test_admin_endpoint_succeeds_for_admin(db_session, jwt_secret, monkeypatch):
+    """Test that admin endpoint succeeds for authenticated admin user."""
+    user_id = "55555555-5555-5555-5555-555555555555"
+    admin_user = User(
+        id=UUID(user_id),
+        email="admin@example.com",
+        is_admin=True,
+    )
+    db_session.add(admin_user)
+    await db_session.commit()
+
+    monkeypatch.setattr(settings, "supabase_jwt_secret", jwt_secret)
+    token = jwt.encode(
+        {
+            "sub": user_id,
+            "email": "admin@example.com",
+            "role": "authenticated",
+            "aud": "authenticated",
+            "exp": int(time.time()) + 3600,
+        },
+        jwt_secret,
+        algorithm="HS256",
+    )
+
+    async with AsyncClient(
+        transport=ASGITransport(app=app),
+        base_url="http://test",
+        headers={"Authorization": f"Bearer {token}"},
+    ) as ac:
+        response = await ac.post(
+            "/games",
+            json={
+                "name": "Test Game",
+                "slug": "test-game",
+                "generation": 1,
+                "region": "Kanto",
+                "category": "core",
+            },
+        )
+    assert response.status_code == 201
+    assert response.json()["name"] == "Test Game"