Harden the API and the data layer after a security and performance audit

Security
- Every route now requires a login and refuses ids outside the caller's
  workspace with 404: plan, leave-wishes, day-overrides and vacation-days
  were fully anonymous; every other router trusted client-supplied
  workspace/child/parent ids. Scraper sessions are bound to their owner.
- Invitations can no longer be created for a foreign workspace, and a
  redeemer who is already a member (or a full workspace) is refused.
- Production refuses the default JWT secret; API docs are hidden in
  production; a failed migration aborts startup instead of serving.
- Login and register no longer reveal whether an email exists; inactive
  accounts are rejected; /auth/refresh is rate limited.
- The FK scraper writes debug artefacts only when explicitly enabled,
  logs no scraped values or page text, clears the BankID QR as soon as it
  is scanned and purges finished sessions after five minutes.
- Real FK page captures are removed from the tree (history rewrite
  follows); the parser tests use a synthetic fixture.

Performance and correctness
- Plan apply/sync run inside one locked transaction with batched writes
  instead of one commit per row, so a failure mid-batch leaves nothing
  half-applied and concurrent syncs no longer corrupt each other.
- SQLite runs in WAL mode with a busy timeout; 14 indexes cover the
  filters that were full scans; argon2 hashing runs off the event loop;
  responses are gzipped.
- Frontend: a 401 now refreshes the token once and retries, so sessions
  no longer die silently after 15 minutes; every data hook discards
  stale responses; logout clears state even when the server call fails.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CsXCCcDfmV4Sps4ZQSvNEY

backend/tests/unit/test_fetch_data_router.py

@@ -28,40 +28,24 @@ non-headless browser as a fire-and-forget background task, which is unsafe
 to do from a router test).
 """
 
-from datetime import datetime
 from typing import Any
-from uuid import UUID, uuid4
+from uuid import UUID
 
-import aiosqlite
 import pytest
 import pytest_asyncio
-from httpx import ASGITransport, AsyncClient
+from httpx import AsyncClient
 
-from app.dependencies import get_connection, get_current_user
-from app.entities.user import User
-from app.main import app
 from app.routers import fetch_data as fetch_data_router
 from tests.conftest import SeededIds
 
 
 @pytest_asyncio.fixture
-async def client(connection: aiosqlite.Connection) -> AsyncClient:
-    """An httpx client against the real app: `get_connection` and
-    `get_current_user` are overridden to use the test's in-memory connection
-    and a fixed fake user.
+async def client(authed_client: AsyncClient) -> AsyncClient:
+    """The shared `seeded_ids`-bound authenticated client (see
+    `tests/conftest.py`) — required now that the routes reject ids outside
+    the caller's workspace. See CLAUDE.md T1 authz work / audit §4.
     """
-    app.dependency_overrides[get_connection] = lambda: connection
-    app.dependency_overrides[get_current_user] = lambda: User(
-        id=uuid4(),
-        personal_data_uuid=uuid4(),
-        email="test@example.com",
-        hashed_password="not-a-real-hash",
-        created_at=datetime.now(),
-    )
-    async with AsyncClient(transport=ASGITransport(app=app), base_url="http://test") as ac:
-        yield ac
-    app.dependency_overrides.pop(get_connection, None)
-    app.dependency_overrides.pop(get_current_user, None)
+    return authed_client
 
 
 def _manual_payload(seeded_ids: SeededIds, **overrides: object) -> dict:
@@ -233,11 +217,17 @@ class TestScraperEndpointsEnabled:
         captured: dict[str, Any] = {}
 
         async def fake_start_session(
-            *, workspace_id: UUID, personal_data_uuid: UUID, child_id: UUID, persist_callback: Any
+            *,
+            workspace_id: UUID,
+            personal_data_uuid: UUID,
+            child_id: UUID,
+            persist_callback: Any,
+            owner_user_id: UUID,
         ) -> str:
             captured["workspace_id"] = workspace_id
             captured["personal_data_uuid"] = personal_data_uuid
             captured["child_id"] = child_id
+            captured["owner_user_id"] = owner_user_id
             return "fake-session-id"
 
         monkeypatch.setattr(fetch_data_router._scraper_service, "start_session", fake_start_session)
@@ -263,7 +253,7 @@ class TestScraperEndpointsEnabled:
     ) -> None:
         monkeypatch.setattr(fetch_data_router.settings, "scraper_enabled", True)
 
-        async def fake_poll_session(session_id: str) -> dict:
+        async def fake_poll_session(session_id: str, owner_user_id: UUID) -> dict:
             assert session_id == "some-session-id"
             return {"status": "awaiting_scan"}
 
@@ -283,7 +273,7 @@ class TestScraperEndpointsEnabled:
 
         cancelled: dict[str, Any] = {}
 
-        async def fake_cancel_session(session_id: str) -> None:
+        async def fake_cancel_session(session_id: str, owner_user_id: UUID) -> None:
             cancelled["session_id"] = session_id
 
         monkeypatch.setattr(