fix(sentry): initialize Sentry after DB settings are loaded in lifespan

Move init_sentry() from module level into the FastAPI lifespan context
manager, immediately after load_settings_from_db() completes. This
ensures that SENTRY_DSN and other Sentry settings configured via the
database admin UI are picked up on every restart.

Also update tests and docs accordingly.

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

app/main.py

@@ -48,10 +48,6 @@ SESSION_SECRET = (
     settings.session_secret or "INSECURE_DEFAULT_FOR_DEVELOPMENT_ONLY_DO_NOT_USE_IN_PRODUCTION_MINIMUM_32_CHARS"
 )
 
-# Initialise Sentry as early as possible so that any startup errors are captured
-init_sentry()
-
-
 @asynccontextmanager
 async def lifespan(app: FastAPI):
     """
@@ -74,6 +70,10 @@ async def lifespan(app: FastAPI):
     finally:
         db.close()
 
+    # Initialize Sentry after DB settings are loaded so that values configured
+    # via the database UI (e.g. SENTRY_DSN) are respected in addition to env vars.
+    init_sentry()
+
     # Ensure OCR language data is available (background download, non-blocking)
     from app.utils.ocr_language_manager import ensure_ocr_languages_async