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/scripts/migrate_db.py

@@ -89,6 +89,17 @@ def migrate_tables():
         """)
         logger.info("Table 'reported_mistakes' ensured to exist.")
         
+        # 4. Update CONTACTS Table (Two-step for SQLite compatibility)
+        logger.info("Checking 'contacts' table schema for unsubscribe_token...")
+        contacts_columns = get_table_columns(cursor, "contacts")
+        
+        if 'unsubscribe_token' not in contacts_columns:
+            logger.info("Adding column 'unsubscribe_token' to 'contacts' table...")
+            cursor.execute("ALTER TABLE contacts ADD COLUMN unsubscribe_token TEXT")
+
+            logger.info("Creating UNIQUE index on 'unsubscribe_token' column...")
+            cursor.execute("CREATE UNIQUE INDEX IF NOT EXISTS idx_contacts_unsubscribe_token ON contacts (unsubscribe_token)")
+
         conn.commit()
         logger.info("All migrations completed successfully.")