Replace process-local session cache with pluggable session cache backend

backend/app/routers/auth.py

@@ -12,7 +12,7 @@ from __future__ import annotations
 import structlog
 from fastapi import APIRouter, HTTPException, Request, Response, status
 
-from app.dependencies import DbDep, SettingsDep, invalidate_session_cache
+from app.dependencies import DbDep, SessionCacheDep, SettingsDep
 from app.models.auth import LoginRequest, LoginResponse, LogoutResponse
 from app.services import auth_service
 
@@ -88,6 +88,7 @@ async def logout(
     response: Response,
     db: DbDep,
     settings: SettingsDep,
+    session_cache: SessionCacheDep,
 ) -> LogoutResponse:
     """Invalidate the active session.
 
@@ -108,8 +109,8 @@ async def logout(
     if token:
         raw_token = await auth_service.logout(db, token, settings.session_secret)
         if raw_token:
-            invalidate_session_cache(raw_token)
-            invalidate_session_cache(token)
+            session_cache.invalidate(raw_token)
+            session_cache.invalidate(token)
     response.delete_cookie(key=_COOKIE_NAME)
     return LogoutResponse()