feat: Implement unsubscribe link for marketing automation [31188f42]

This commit introduces a new unsubscribe feature to allow contacts to opt-out
from marketing automation.

Key changes include:
- Database schema migration: Added  (UUID) to the  model.
- Data population: Implemented a script to assign unique tokens to existing contacts.
- API endpoint: Created a public GET  endpoint to handle opt-out requests.
- Automation: New contacts automatically receive an unsubscribe token upon creation.
- Integration: The full unsubscribe link is now returned via the provisioning API
  for storage in SuperOffice UDFs (ProgID: SuperOffice:9).
- Documentation: Updated  and
  to reflect the new feature and its integration requirements.
- Added  for quick overview and next steps.

company-explorer/backend/config.py

@@ -24,6 +24,9 @@ try:
         # Paths
         LOG_DIR: str = "/app/Log_from_docker"
 
+        # Public URL
+        APP_BASE_URL: str = "http://localhost:8090"
+
         class Config:
             env_file = ".env"
             extra = 'ignore'