feat(system-reset): add system reset and factory reset feature

- Add FACTORY_RESET_ON_STARTUP and ENABLE_FACTORY_RESET config settings
- Create app/utils/system_reset.py with core reset logic (wipe DB + files, reimport)
- Create app/api/system_reset.py with admin-only API endpoints
- Create app/views/system_reset.py with admin-only UI view
- Create frontend/templates/system_reset.html with confirmation dialogs
- Auto-reset on startup when FACTORY_RESET_ON_STARTUP=true
- Re-import uses watch folder mechanism for re-ingestion
- Register routers in API and views init files
- Add i18n keys and SETTING_METADATA entries
- Add nav links in base.html (desktop + mobile)

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

.env.demo

@@ -7,6 +7,10 @@ GOTENBERG_URL=http://gotenberg:3000
 ALLOW_FILE_DELETE=true  # Allow deletion of file records
 COMPLIANCE_ENABLED=true  # Enable compliance templates dashboard (GDPR, HIPAA, SOC 2)
 
+# **System Reset / Factory Reset**
+# FACTORY_RESET_ON_STARTUP=false  # Wipe all user data on every startup (demo/testing only)
+# ENABLE_FACTORY_RESET=false      # Show the System Reset page in admin UI
+
 # **Logging**
 # LOG_LEVEL controls the Python root-logger level.
 # Accepted values: DEBUG, INFO, WARNING, ERROR, CRITICAL (default: INFO).