Document task DB access and unify background task DB handling

backend/app/tasks/geo_cache_flush.py

@@ -11,21 +11,19 @@ at risk on an unexpected process restart.
 
 from __future__ import annotations
 
-from typing import TYPE_CHECKING, Any
+from typing import TYPE_CHECKING
 
 import structlog
 
-from app.db import open_db
+from app.services import geo_service
+from app.tasks.db import task_db
 from app.utils.runtime_state import get_effective_settings
 
-if TYPE_CHECKING:
-    import aiosqlite
-    from app.config import Settings
-from app.services import geo_service
-
 if TYPE_CHECKING:
     from fastapi import FastAPI
 
+    from app.config import Settings
+
 log: structlog.stdlib.BoundLogger = structlog.get_logger()
 
 #: How often the flush job fires (seconds).  Configurable tuning constant.
@@ -35,23 +33,14 @@ GEO_FLUSH_INTERVAL: int = 60
 JOB_ID: str = "geo_cache_flush"
 
 
-async def _get_db(settings: "Settings") -> tuple[aiosqlite.Connection, bool]:
-    db = await open_db(settings.database_path)
-    return db, True
-
-
-async def _run_flush_with_settings(settings: "Settings") -> None:
+async def _run_flush_with_settings(settings: Settings) -> None:
     """Flush the geo service dirty set to the application database.
 
     Args:
         settings: The resolved application settings used for database access.
     """
-    db, close_db = await _get_db(settings)
-    try:
+    async with task_db(settings) as db:
         count = await geo_service.flush_dirty(db)
-    finally:
-        if close_db:
-            await db.close()
 
     if count > 0:
         log.debug("geo_cache_flush_ran", flushed=count)