v0.141.0: F6 initialize-to-usable (detached crash-safe init job + status poll) + F7 Vissza back-routes

- F6: POST /api/storage/init runs format→mount→register as a DETACHED single-flight job (context.Background, netAddState shape) the wizard polls via GET /api/storage/init/status; 3-step progress; register-last marker-last crash-safety. Fixes the client-disconnect-aborts-mount bug. No agent change (chain reaches FileBrowser sync = controller-only). Red-proof TestStorageInit_DetachedSurvivesClientDisconnect.
- F7: storage_init/attach Vissza → /storage (was /settings). Test TestStorageWizardBackAnchors_PointToStorage.

controller/internal/web/templates/storage_attach.html

@@ -3,7 +3,7 @@
 
 <div class="page-header">
     <div style="display:flex;align-items:center;gap:.5rem">
-        <a href="/settings" class="btn btn-sm btn-outline">← Vissza</a>
+        <a href="/storage" class="btn btn-sm btn-outline">← Vissza</a>
         <h2>Meglévő meghajtó csatolása</h2>
     </div>
 </div>