build(deps): bump alembic from 1.16.5 to 1.18.4

Bumps [alembic](https://github.com/sqlalchemy/alembic) from 1.16.5 to 1.18.4.
- [Release notes](https://github.com/sqlalchemy/alembic/releases)
- [Changelog](https://github.com/sqlalchemy/alembic/blob/main/CHANGES)
- [Commits](https://github.com/sqlalchemy/alembic/commits)

---
updated-dependencies:
- dependency-name: alembic
  dependency-version: 1.18.4
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements.txt

@@ -1,4 +1,4 @@
-alembic==1.16.5
+alembic==1.18.4
 annotated-types==0.7.0
 anyio==4.12.1
 certifi==2026.1.4