Add `SetDefaultValues()` call to ensure PageSize is bounded, preventing
potential excessive memory allocation from unbounded pagination
parameters.
Fixes CodeQL alert
[#188](https://github.com/go-gitea/gitea/security/code-scanning/188).
All other 49 open alerts were false-positives and are dismissed with
appropriate comments.
Co-authored-by: Claude (Opus 4.6) <noreply@anthropic.com>