fix(db): do not log the database password

[dimoschi]

Types of changes

• Bugfix (non-breaking change which fixes an issue).
• New feature (non-breaking change which adds functionality).
• Breaking change (fix or feature that would cause existing functionality not to work as expected).
• Documentation Update (if none of the other choices applies).

Proposed changes

src/database/session.py logged the full connection string at DEBUG, password included. It now logs the engine URL with repr(), which masks the password:

Database URL: mariadb+asyncmy://bot:***@localhost:3306/bot_dev?charset=utf8mb4

Checklist

• I have read and followed the CONTRIBUTING.md
  doc.
• Lint and unit tests pass locally with my changes.
• I have added the necessary documentation (if appropriate).

Additional context

tests/src/database/test_session.py reloads the module with a known password and checks that it does not appear in the logs. It failed before the fix.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 68.17%. Comparing base (fe68e1c) to head (736eddb).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #204   +/-   ##
=======================================
  Coverage   68.17%   68.17%           
=======================================
  Files          78       78           
  Lines        3702     3702           
=======================================
  Hits         2524     2524           
  Misses       1178     1178           

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