fire-planner: lazy-refresh /networth from wf_sync (default TTL 1d)

The account_snapshot cache fed /networth, /networth/history, and
/scenarios/{id}/progress. No CronJob populated it, so the cache had
drifted ~18 days behind the wealthfolio_sync mirror (last refresh
2026-05-09 via manual kubectl exec; Grafana reads wf_sync directly
and stayed fresh).

Switch to lazy refresh on read: each request to those endpoints now
checks MAX(account_snapshot.snapshot_date) — if it's older than
NETWORTH_CACHE_TTL_DAYS (default 1), pull fresh rows from wf_sync via
read_account_snapshots_from_pg and upsert. Idempotent under
concurrency (existing ON CONFLICT DO UPDATE).

Plumbing:
- Add get_wf_sync_session dependency that yields None when the wf_sync
  factory isn't wired (keeps existing tests' behaviour: no refresh
  attempted, they continue to seed account_snapshot directly).
- Wire wf_sync engine + session_factory in app.lifespan when
  WEALTHFOLIO_SYNC_DB_CONNECTION_STRING is set.
- Centralise the staleness check in refresh_account_snapshots_if_stale.

Tests:
- 271 existing tests still green.
- Three new tests in test_api_networth_refresh.py covering: empty cache
  triggers refresh, stale cache triggers refresh, fresh cache skips
  refresh (asserts the wf_sync value is NOT served).

fire_planner/api/progress.py

@@ -16,7 +16,7 @@ from fastapi import APIRouter, Depends, HTTPException
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
-from fire_planner.api.dependencies import get_session
+from fire_planner.api.dependencies import get_session, get_wf_sync_session
 from fire_planner.api.schemas import (
     ProgressActualPoint,
     ProgressProjectedPoint,
@@ -24,6 +24,7 @@ from fire_planner.api.schemas import (
     ProgressVariancePoint,
 )
 from fire_planner.db import AccountSnapshot, McRun, ProjectionYearly, Scenario
+from fire_planner.ingest.wealthfolio import refresh_account_snapshots_if_stale
 
 router = APIRouter(prefix="/scenarios", tags=["progress"])
 
@@ -32,11 +33,13 @@ router = APIRouter(prefix="/scenarios", tags=["progress"])
 async def get_progress(
     scenario_id: int,
     session: AsyncSession = Depends(get_session),
+    wf_sync: AsyncSession | None = Depends(get_wf_sync_session),
 ) -> ProgressResponse:
     scen = await session.get(Scenario, scenario_id)
     if scen is None:
         raise HTTPException(status_code=404, detail="Scenario not found")
 
+    await refresh_account_snapshots_if_stale(session, wf_sync)
     actuals_rows = (await session.execute(
         select(
             AccountSnapshot.snapshot_date,