Refactor and reorganize Alembic and database configuration.

Moved Alembic files into the `app/alembic` directory and updated related paths. Consolidated database configuration in `config.py`, leveraging environment variables and ensuring centralized management. Updated Docker Compose to include `.env` files, providing a more consistent environment setup.

backend/app/alembic/versions/7396957cbe80_initial_empty_migration.py

@@ -0,0 +1,26 @@
+"""Initial empty migration
+
+Revision ID: 7396957cbe80
+Revises: 
+Create Date: 2025-02-27 12:47:46.445313
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = '7396957cbe80'
+down_revision: Union[str, None] = None
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    pass
+
+
+def downgrade() -> None:
+    pass