chore: baseline snapshot before moderation-strictness feature

Repo .git was damaged (refs/ missing, index truncated, object store near-empty).
Repaired via git init (rebuilt refs), stale index preserved as .git/index.corrupt-20260910.bak,
then full worktree committed as a rollback baseline.

templates/maintenance-mode.html

@@ -0,0 +1,8 @@
+{{template "base/header" .}}
+<div class="uk-card uk-card-default uk-card-body">
+    <h2>{{t .LangCode "maintenance.title"}}</h2>
+    <div>
+        <p>{{t .LangCode "maintenance.desc"}}</p>
+    </div>
+</div>
+{{template "base/footer" .}}