fix: remove double-call on AsyncSession in SerieScanner

get_async_session_factory() returns session directly, not factory.
Calling result again with () caused 'AsyncSession' object is not callable.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

docs/DEVELOPMENT.md

@@ -181,6 +181,22 @@ scheduler = AsyncIOScheduler(jobstores=jobstores)
 
 **If server is down >1 hour:** No automatic recovery. Manual trigger via `POST /api/scheduler/trigger-rescan` or wait for next scheduled run.
 
+### Database Session Management
+
+`get_async_session_factory()` returns a **new AsyncSession instance** directly (not a factory). The function name is historical — callers receive the session immediately:
+
+```python
+# Correct usage:
+db = get_async_session_factory()  # db IS the session
+await db.execute(...)
+await db.commit()
+await db.close()
+```
+
+Do NOT call the result again with `()` — that tries to call an `AsyncSession` object, causing `'AsyncSession' object is not callable`.
+
+For context manager usage, prefer `get_db_session()` (auto-commits) or `get_transactional_session()` (manual commit).
+
 ### Health Check Endpoints
 
 The application provides health check endpoints for monitoring and container orchestration:

src/core/SerieScanner.py

@@ -218,8 +218,7 @@ class SerieScanner:
         try:
             from src.server.database.connection import get_async_session_factory
 
-            session_factory = get_async_session_factory()
-            db = session_factory()
+            db = get_async_session_factory()
             try:
                 existing = await AnimeSeriesService.get_by_key(db, serie.key)
                 if existing:

tests/unit/test_serie_scanner_db_writes.py

@@ -209,7 +209,7 @@ class TestPersistSerieToDbErrorHandling:
 
         with patch(
             "src.server.database.connection.get_async_session_factory",
-            return_value=mock_factory
+            return_value=mock_session
         ):
             with patch(
                 "src.server.database.service.AnimeSeriesService.get_by_key",