feat(settings): per-option save, live worker sync, audit log, and rollback

A) Per-option Save Button
- Add per-setting Save button in settings.html (visible only when value changed)
- Button calls POST /api/settings/{key} directly; existing bulk Save retained
- Add Audit Log link in settings page header

B) Immediate Worker Sync
- New app/utils/settings_sync.py with notify_settings_updated() (Redis version key)
  and register_settings_reload_signal() (Celery task_prerun handler)
- Register signal in celery_worker.py at startup
- All API write paths call notify_settings_updated() after successful saves

C) Audit Log
- Add SettingsAuditLog model (key, old_value, new_value, changed_by, changed_at, action)
- save_setting_to_db / delete_setting_from_db accept changed_by and write audit entries
- New get_audit_log() service function (masks sensitive values)
- New GET /api/settings/audit-log endpoint (admin-only)
- New GET /admin/settings/audit-log view + audit_log.html template
- Visible to all admins (per clarified requirement)

D) Config Rollback / History
- New get_setting_history() and rollback_setting() service functions
- New GET /api/settings/{key}/history endpoint
- New POST /api/settings/{key}/rollback/{history_id} endpoint
- Rollback buttons in audit_log.html with confirmation dialog
- Tests: 25 new tests covering audit log, rollback, worker sync helpers, and API endpoints

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

app/celery_worker.py

@@ -3,30 +3,32 @@
 from celery.schedules import crontab
 
 # Ensure tasks are loaded
-from app import tasks  # noqa: F401 - Imports app/tasks.py so Celery can register tasks
-
+from app import \
+    tasks  # noqa: F401 - Imports app/tasks.py so Celery can register tasks
 # Import the shared Celery instance
 from app.celery_app import celery
 from app.config import settings
 from app.tasks.check_credentials import check_credentials
 from app.tasks.convert_to_pdf import convert_to_pdf  # noqa: F401
-from app.tasks.embed_metadata_into_pdf import embed_metadata_into_pdf  # noqa: F401
-from app.tasks.extract_metadata_with_gpt import extract_metadata_with_gpt  # noqa: F401
+from app.tasks.embed_metadata_into_pdf import \
+    embed_metadata_into_pdf  # noqa: F401
+from app.tasks.extract_metadata_with_gpt import \
+    extract_metadata_with_gpt  # noqa: F401
 from app.tasks.imap_tasks import pull_all_inboxes  # noqa: F401
 from app.tasks.monitor_stalled_steps import monitor_stalled_steps  # noqa: F401
-
 # **Ensure all tasks are imported before Celery starts**
 from app.tasks.process_document import process_document  # noqa: F401
-from app.tasks.process_with_azure_document_intelligence import process_with_azure_document_intelligence  # noqa: F401
+from app.tasks.process_with_azure_document_intelligence import \
+    process_with_azure_document_intelligence  # noqa: F401
 from app.tasks.refine_text_with_gpt import refine_text_with_gpt  # noqa: F401
 from app.tasks.rotate_pdf_pages import rotate_pdf_pages  # noqa: F401
 from app.tasks.send_to_all import send_to_all_destinations  # noqa: F401
-
 # Import new send tasks
 from app.tasks.upload_to_dropbox import upload_to_dropbox  # noqa: F401
 from app.tasks.upload_to_email import upload_to_email  # noqa: F401
 from app.tasks.upload_to_ftp import upload_to_ftp  # noqa: F401
-from app.tasks.upload_to_google_drive import upload_to_google_drive  # noqa: F401
+from app.tasks.upload_to_google_drive import \
+    upload_to_google_drive  # noqa: F401
 from app.tasks.upload_to_nextcloud import upload_to_nextcloud  # noqa: F401
 from app.tasks.upload_to_onedrive import upload_to_onedrive  # noqa: F401
 from app.tasks.upload_to_paperless import upload_to_paperless  # noqa: F401
@@ -34,6 +36,10 @@ from app.tasks.upload_to_s3 import upload_to_s3  # noqa: F401
 from app.tasks.upload_to_sftp import upload_to_sftp  # noqa: F401
 from app.tasks.upload_to_webdav import upload_to_webdav  # noqa: F401
 from app.tasks.uptime_kuma_tasks import ping_uptime_kuma  # noqa: F401
+# Register the settings reload signal handler so workers pick up config changes
+from app.utils.settings_sync import register_settings_reload_signal
+
+register_settings_reload_signal()
 
 celery.conf.task_routes = {
     "app.tasks.*": {"queue": "default"},
@@ -89,4 +95,6 @@ celery.conf.beat_schedule = {
 }
 
 # Remove None entries from beat_schedule
-celery.conf.beat_schedule = {k: v for k, v in celery.conf.beat_schedule.items() if v is not None}
+celery.conf.beat_schedule = {
+    k: v for k, v in celery.conf.beat_schedule.items() if v is not None
+}