Fix review submission from single-commit PR view (#37475) (#37485)

Backport #37475 by @cyphercodes

Fixes #37415.

Pin the review submission form action to the canonical PR files route

Co-authored-by: Rayan Salhab <r.salhab@aiyexpertsolutions.com>
Co-authored-by: cyphercodes <cyphercodes@users.noreply.github.com>
Co-authored-by: Hermes Agent (OpenAI GPT-5.5) <noreply@nousresearch.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

templates/repo/diff/new_review.tmpl

@@ -11,7 +11,7 @@
 {{if $.IsShowingAllCommits}}
 <div class="review-box-panel tippy-target">
 	<div class="ui segment">
-		<form class="ui form form-fetch-action" action="{{.Link}}/reviews/submit" method="post">
+		<form class="ui form form-fetch-action" action="{{.Issue.Link}}/files/reviews/submit" method="post">
 			<input type="hidden" name="commit_id" value="{{.AfterCommitID}}">
 			<div class="field flex-text-block">
 				<div class="tw-flex-1">{{ctx.Locale.Tr "repo.diff.review.header"}}</div>