chore(deps): bump sqlalchemy from 2.0.48 to 2.0.49 in /backend

Bumps [sqlalchemy](https://github.com/sqlalchemy/sqlalchemy) from 2.0.48 to 2.0.49.
- [Release notes](https://github.com/sqlalchemy/sqlalchemy/releases)
- [Changelog](https://github.com/sqlalchemy/sqlalchemy/blob/main/CHANGES.rst)
- [Commits](https://github.com/sqlalchemy/sqlalchemy/commits)

---
updated-dependencies:
- dependency-name: sqlalchemy
  dependency-version: 2.0.49
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

backend/requirements.txt

@@ -5,7 +5,7 @@ pydantic==2.12.5
 pydantic-settings==2.13.1
 
 # Database
-sqlalchemy==2.0.48  # Updated: Fixed Python 3.14 incompatibility with TypingOnly assertion (was 2.0.25)
+sqlalchemy==2.0.49  # Updated: Fixed Python 3.14 incompatibility with TypingOnly assertion (was 2.0.25)
 alembic==1.18.4
 psycopg2-binary==2.9.11
 asyncpg==0.31.0