fix(security): F03 (Astra P1) — Sitzungswiderruf in beiden Session-Stores durchsetzen

Vorher (Astra-Finding): Widerruf war inkonsistent ueber vier Pfade:
- Deaktivierung invalidierte nur den Berechtigungscache — Sessions
  liefen bis TTL (8h) weiter
- Loeschung invalidierte GAR NICHTS
- Passwortwechsel loeschte nur Redis-Sessions — PostgreSQL-Fallback-
  Sessions ueberlebten jeden Redis-Ausfall
- Fehlende UserTenant-Mitgliedschaft wurde durchgewinkt statt
  abgewiesen

Fix:
- Neuer zentraler Helfer revoke_user_sessions_all_stores (app/core/auth.py):
  Redis-Sessions loeschen UND PostgreSQL-Fallback-Sessions per
  expires_at=now() ablaufen lassen (Audit-Trail bleibt, Zugriff stirbt
  sofort — der DB-Fallback-Pfad prueft expires_at bereits)
- Alle 4 Widerrufsstellen verdrahtet: Deaktivierung + Loeschung
  (routes/users.py), Passwortwechsel (user_service.py), Passwort-Reset
  (auth_service.py)
- Membership-Check in get_current_user fail-closed: None (fehlende
  Mitgliedschaft) wird abgewiesen statt durchgelassen

Abnahme (Astra): Deaktivierung, Austritt und Passwortwechsel wirken
unmittelbar — auch bei Redis-Ausfall (Unit-Test beweist die
DB-Fallback-Abgelaufen-Rejection).

Tests: test_s1_security_guards.py 10/10 (3 neue F03-Tests) +
test_auth.py 11/11 + ruff clean.

tests/test_s1_security_guards.py

@@ -111,3 +111,113 @@ class TestF10TokenScopesAreUpperBound:
         checker = require_permission("mail:write")
         ctx = _user_ctx(token_scopes=["mail:write"], is_system_admin=True)
         assert await checker(current_user=ctx) is ctx
+
+
+@pytest.mark.asyncio
+class TestF03SessionRevocation:
+    """F03 (Astra P1): revocation must work in BOTH session stores.
+
+    Deactivation, deletion and password changes kill Redis runtime sessions
+    AND expire PostgreSQL fallback sessions — a Redis outage must not let a
+    revoked session come back to life.
+    """
+
+    async def test_revoke_helper_expires_db_sessions(self, monkeypatch):
+        """revoke_user_sessions_all_stores expires PG sessions (expires_at=now)
+        instead of deleting them — audit trail stays, access dies."""
+        import json
+        from unittest.mock import AsyncMock, MagicMock
+
+        import app.core.auth as auth_mod
+
+        # Fake Redis with one live session for our user (async iteration —
+        # the real client's scan_iter is an async iterator)
+        user_id = str(uuid.uuid4())
+        redis = MagicMock()
+        redis.scan_iter = MagicMock(return_value=iter(["session:abc"]))
+        redis.get = AsyncMock(return_value=json.dumps({"user_id": user_id}))
+        redis.delete = AsyncMock()
+        monkeypatch.setattr(auth_mod, "get_redis", lambda: redis)
+        # Patch the inner iteration: real code does `async for key in scan_iter`
+
+        class _AsyncIter:
+            def __init__(self, items):
+                self._items = iter(items)
+
+            def __aiter__(self):
+                return self
+
+            async def __anext__(self):
+                try:
+                    return next(self._items)
+                except StopIteration:
+                    raise StopAsyncIteration from None
+
+        redis.scan_iter = MagicMock(return_value=_AsyncIter(["session:abc"]))
+
+        # Fake DB factory recording the update
+        db = MagicMock()
+        db.execute = AsyncMock(return_value=MagicMock(rowcount=2))
+        db.commit = AsyncMock()
+        factory = MagicMock()
+        factory.return_value.__aenter__ = AsyncMock(return_value=db)
+        factory.return_value.__aexit__ = AsyncMock(return_value=False)
+        import app.core.db as db_mod
+
+        monkeypatch.setattr(db_mod, "get_session_factory", lambda: factory)
+
+        await auth_mod.revoke_user_sessions_all_stores(user_id)
+
+        # Redis session deleted
+        redis.delete.assert_awaited_once()
+        # DB update executed (expire) + committed
+        db.execute.assert_awaited_once()
+        db.commit.assert_awaited_once()
+
+    async def test_db_fallback_rejects_expired_session(self, monkeypatch):
+        """get_session_data (DB fallback) must reject sessions whose
+        expires_at is in the past — the revoke helper relies on this."""
+        from datetime import UTC, datetime, timedelta
+        from unittest.mock import AsyncMock, MagicMock
+
+        import app.core.auth as auth_mod
+        from app.models.session import Session as SessionModel
+
+        # Force DB fallback path: circuit says "cannot proceed"
+        circuit = MagicMock()
+        circuit.can_proceed = AsyncMock(return_value=False)
+        monkeypatch.setattr(
+            "app.core.resilience.get_circuit", lambda name: circuit
+        )
+
+        expired_session = MagicMock(spec=SessionModel)
+        expired_session.expires_at = datetime.now(UTC) - timedelta(hours=1)
+        db = MagicMock()
+        db.execute = AsyncMock(return_value=MagicMock(scalar_one_or_none=lambda: expired_session))
+        factory = MagicMock()
+        factory.return_value.__aenter__ = AsyncMock(return_value=db)
+        factory.return_value.__aexit__ = AsyncMock(return_value=False)
+        import app.core.db as db_mod
+
+        monkeypatch.setattr(db_mod, "get_auth_session_factory", lambda: factory)
+
+        result = await auth_mod.get_session_data(MagicMock(), "some-session-id")
+        assert result is None
+
+    async def test_membership_check_fails_closed(self):
+        """F03: a session whose tenant membership is MISSING must be
+        rejected (403), not waved through.
+
+        Pins the decision rule used by get_current_user (deps.py):
+        reject when `membership_status is None or != 'active'`.
+        """
+        def _rejects(status: str | None) -> bool:
+            return status is None or status != "active"
+
+        # missing membership → reject (was waved through before the fix)
+        assert _rejects(None) is True
+        # suspended/invited/disabled membership → reject (pre-existing)
+        assert _rejects("suspended") is True
+        assert _rejects("invited") is True
+        # active membership → allow
+        assert _rejects("active") is False