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/server.go

@@ -92,7 +92,8 @@ type Server struct {
 
 	// NAS add orchestration (verify-before-commit): the single-flight job slot + the two seams.
 	// netAgentFn nil → the shared agentClient(); netProbeFn nil → runNetProbe (the uid-1000 re-exec).
-	netAdd     netAddState
+	netAdd      netAddState
+	storageInit storageInitState
 	netAgentFn func() (netAgent, error)
 	// fabUpload is the chunked browser .fab upload single-flight slot (v0.128.0).
 	fabUpload uploadState