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/app/routers/plan.py

@@ -9,7 +9,7 @@ PLANNING_ENGINE_SPEC.md §4.
 
 from fastapi import APIRouter, HTTPException, status
 
-from app.dependencies import PlanningEngineServiceDep, PlanningServiceDep
+from app.dependencies import PlanningEngineServiceDep, PlanningServiceDep, WorkspaceScopeDep
 from app.models.plan import (
     PlanApplyRequest,
     PlanApplyResponse,
@@ -25,9 +25,10 @@ router = APIRouter(prefix="/api/plan", tags=["plan"])
 
 @router.post("/propose", response_model=PlanProposalResponse)
 async def propose_plan(
-    payload: PlanProposeRequest, service: PlanningEngineServiceDep
+    payload: PlanProposeRequest, service: PlanningEngineServiceDep, scope: WorkspaceScopeDep
 ) -> PlanProposalResponse:
     """Compute a plan proposal. Read-only — persists nothing, safe to spam."""
+    scope.check_workspace(payload.workspace_id)
     try:
         proposal = await service.propose(payload.workspace_id)
     except NotFoundError as exc:
@@ -38,7 +39,9 @@ async def propose_plan(
 
 
 @router.post("/apply", response_model=PlanApplyResponse)
-async def apply_plan(payload: PlanApplyRequest, service: PlanningServiceDep) -> PlanApplyResponse:
+async def apply_plan(
+    payload: PlanApplyRequest, service: PlanningServiceDep, scope: WorkspaceScopeDep
+) -> PlanApplyResponse:
     """Accept a (possibly user-edited) set of proposed days as real plan.
 
     Always returns 200 with `accepted: false` and a `rejections`/`collisions`
@@ -48,6 +51,15 @@ async def apply_plan(payload: PlanApplyRequest, service: PlanningServiceDep) ->
     A genuinely missing workspace/child (404) is the one case still raised
     as an HTTP error, since that's not something the batch report can explain.
     """
+    scope.check_workspace(payload.workspace_id)
+    # Every child/parent named in the batch must belong to the caller's own
+    # workspace too — otherwise a forged child_id/parent_personal_data_uuid
+    # could write a planned_leave_day row attributed to another tenant's
+    # child or parent even though workspace_id itself checks out.
+    for child_id in {item.child_id for item in payload.days}:
+        await scope.check_child(child_id)
+    for parent_id in {item.parent_personal_data_uuid for item in payload.days}:
+        await scope.check_member(parent_id)
     try:
         result = await service.apply_proposed_days(
             workspace_id=payload.workspace_id,
@@ -60,7 +72,9 @@ async def apply_plan(payload: PlanApplyRequest, service: PlanningServiceDep) ->
 
 
 @router.post("/sync", response_model=PlanSyncResponse)
-async def sync_plan(payload: PlanSyncRequest, service: PlanningServiceDep) -> PlanSyncResponse:
+async def sync_plan(
+    payload: PlanSyncRequest, service: PlanningServiceDep, scope: WorkspaceScopeDep
+) -> PlanSyncResponse:
     """Recompute and persist a workspace's plan in one step.
 
     The direct-manipulation calendar UX's one call: no separate preview
@@ -70,6 +84,7 @@ async def sync_plan(payload: PlanSyncRequest, service: PlanningServiceDep) -> Pl
     can show e.g. "Sommar 2028 flyttades 2 dagar — Ångra" instead of
     silently rewriting the calendar.
     """
+    scope.check_workspace(payload.workspace_id)
     try:
         result = await service.sync_plan(payload.workspace_id)
     except NotFoundError as exc: