Clean up Alembic migrations

- Removed outdated and redundant Alembic migration files to streamline the migration directory. This improves maintainability and eliminates duplicate or unused scripts.

backend/alembic.ini

@@ -2,6 +2,13 @@
 script_location = app/alembic
 sqlalchemy.url = postgresql://postgres:postgres@db:5432/app
 
+# Use sequential naming: 0001_message.py, 0002_message.py, etc.
+# The rev_id is still used internally but filename is cleaner
+file_template = %%(rev)s_%%(slug)s
+
+# Allow specifying custom revision IDs via --rev-id flag
+revision_environment = true
+
 [loggers]
 keys = root,sqlalchemy,alembic