Fix project filter bugs (#26490)
related: #26012
### Bugs
1. missing project filter on the issue page.
https://github.com/go-gitea/gitea/blob/1e76a824bcd71acd59cdfb2c4547806bc34b3d86/modules/indexer/issues/dboptions.go#L11-L15
3. incorrect SQL condition: some issue does not belong to a project but
exists on the project_issue table.
https://github.com/go-gitea/gitea/blob/f5dbac9d36f1678b928bee04e85fbd045c725698/models/issues/issue_search.go#L233
### Before:

### After:

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Co-authored-by: Giteabot <teabot@gitea.io>
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