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:

![before](https://github.com/go-gitea/gitea/assets/50507092/1dcde39e-3e2f-4151-b2c6-4d67bf493c2f)

### After:

![after](https://github.com/go-gitea/gitea/assets/50507092/badfb81f-056d-4a2f-9838-1cba9c15768d)

---------

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

models/issues/issue_stats.go

@@ -133,10 +133,7 @@ func getIssueStatsChunk(opts *IssuesOptions, issueIDs []int64) (*IssueStats, err
 
 		applyMilestoneCondition(sess, opts)
 
-		if opts.ProjectID > 0 {
-			sess.Join("INNER", "project_issue", "issue.id = project_issue.issue_id").
-				And("project_issue.project_id=?", opts.ProjectID)
-		}
+		applyProjectCondition(sess, opts)
 
 		if opts.AssigneeID > 0 {
 			applyAssigneeCondition(sess, opts.AssigneeID)