Add API endpoint to reply to pull request review comments (#36683)

Adds a dedicated endpoint for replying to pull request review comments,

```
POST /repos/{owner}/{repo}/pulls/{index}/comments/{id}/replies
{ "body": "..." }
```

The reply is threaded under the same review as the parent comment.

Ref: https://gitea.com/gitea/gitea-mcp/issues/129
Fixes: https://github.com/go-gitea/gitea/issues/37419
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: Nicolas <bircni@icloud.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/api/v1/swagger/options.go

@@ -168,6 +168,9 @@ type swaggerParameterBodies struct {
 	// in:body
 	CreatePullReviewComment api.CreatePullReviewComment
 
+	// in:body
+	CreatePullReviewCommentReplyOptions api.CreatePullReviewCommentReplyOptions
+
 	// in:body
 	SubmitPullReviewOptions api.SubmitPullReviewOptions