ui: P2R-09 auto-init UX — init line in chrome + danger-zone re-init

Latest 'init' job status surfaced under the host-detail vitals strip
(succeeded/failed/running/queued, with link to the live job log on
non-success). New POST /hosts/{id}/repo/reinit handler dispatches a
fresh init job after the operator types the host name to confirm;
audit row records 'host.repo_reinit'.

web/templates/pages/host_repo.html

@@ -238,8 +238,16 @@
             <span class="mono text-ink-mid">secrets.enc</span> is reused.
           </p>
         </div>
-        <button class="btn btn-danger btn-lg flex-none" disabled
-                title="re-init flow lands in P2R-09">Re-init repo…</button>
+        <form method="post" action="/hosts/{{$host.ID}}/repo/reinit"
+              class="flex-none flex flex-col items-end" style="gap: 8px;"
+              onsubmit="return confirm('Re-initialise the repo on host &quot;{{$host.Name}}&quot;? Existing snapshots are lost if the rest-server allows the wipe; restic refuses if it sees a config file already there.');">
+          <input type="text" name="confirm_hostname" required autocomplete="off"
+                 placeholder="type hostname to confirm"
+                 class="input mono"
+                 style="width: 240px; height: 30px; padding: 0 8px; font-size: 12px;">
+          <button type="submit" class="btn btn-danger btn-lg whitespace-nowrap"
+                  {{if eq $host.Status "online"}}{{else}}disabled title="host is offline"{{end}}>Re-init repo…</button>
+        </form>
       </div>
     </div>
   </div>