feat: Stage 2 — authentication and setup flow

Backend (tasks 2.1–2.6, 2.10):
- settings_repo: get/set/delete/get_all CRUD for the key-value settings table
- session_repo: create/get/delete/delete_expired for session rows
- setup_service: bcrypt password hashing, one-time-only enforcement,
  run_setup() / is_setup_complete() / get_password_hash()
- auth_service: login() with bcrypt verify + token creation,
  validate_session() with expiry check, logout()
- setup router: GET /api/setup (status), POST /api/setup (201 / 409)
- auth router: POST /api/auth/login (token + HttpOnly cookie),
               POST /api/auth/logout (clears cookie, idempotent)
- SetupRedirectMiddleware: 307 → /api/setup for all API paths until setup done
- require_auth dependency: cookie or Bearer token → Session or 401
- conftest.py: manually bootstraps app.state.db for router tests
  (ASGITransport does not trigger ASGI lifespan)
- 85 tests pass; ruff 0 errors; mypy --strict 0 errors

Frontend (tasks 2.7–2.9):
- types/auth.ts, types/setup.ts, api/auth.ts, api/setup.ts
- AuthProvider: sessionStorage-backed context (isAuthenticated, login, logout)
- RequireAuth: guard component → /login?next=<path> when unauthenticated
- SetupPage: Fluent UI form, client-side validation, inline errors
- LoginPage: single password input, ?next= redirect after success
- DashboardPage: placeholder (full impl Stage 5)
- App.tsx: full route tree (/setup, /login, /, *)

backend/app/routers/setup.py

@@ -0,0 +1,71 @@
+"""Setup router.
+
+Exposes the ``POST /api/setup`` endpoint for the one-time first-run
+configuration wizard.  Once setup has been completed, subsequent calls
+return ``409 Conflict``.
+"""
+
+from __future__ import annotations
+
+import structlog
+from fastapi import APIRouter, HTTPException, status
+
+from app.dependencies import DbDep
+from app.models.setup import SetupRequest, SetupResponse, SetupStatusResponse
+from app.services import setup_service
+
+log: structlog.stdlib.BoundLogger = structlog.get_logger()
+
+router = APIRouter(prefix="/api/setup", tags=["setup"])
+
+
+@router.get(
+    "",
+    response_model=SetupStatusResponse,
+    summary="Check whether setup has been completed",
+)
+async def get_setup_status(db: DbDep) -> SetupStatusResponse:
+    """Return whether the initial setup wizard has been completed.
+
+    Returns:
+        :class:`~app.models.setup.SetupStatusResponse` with ``completed``
+        set to ``True`` if setup is done, ``False`` otherwise.
+    """
+    done = await setup_service.is_setup_complete(db)
+    return SetupStatusResponse(completed=done)
+
+
+@router.post(
+    "",
+    response_model=SetupResponse,
+    status_code=status.HTTP_201_CREATED,
+    summary="Run the initial setup wizard",
+)
+async def post_setup(body: SetupRequest, db: DbDep) -> SetupResponse:
+    """Persist the initial BanGUI configuration.
+
+    Args:
+        body: Setup request payload validated by Pydantic.
+        db: Injected aiosqlite connection.
+
+    Returns:
+        :class:`~app.models.setup.SetupResponse` on success.
+
+    Raises:
+        HTTPException: 409 if setup has already been completed.
+    """
+    if await setup_service.is_setup_complete(db):
+        raise HTTPException(
+            status_code=status.HTTP_409_CONFLICT,
+            detail="Setup has already been completed.",
+        )
+
+    await setup_service.run_setup(
+        db,
+        master_password=body.master_password,
+        database_path=body.database_path,
+        fail2ban_socket=body.fail2ban_socket,
+        timezone=body.timezone,
+        session_duration_minutes=body.session_duration_minutes,
+    )
+    return SetupResponse()