feat(imap): resilient batched sync, stale-session cleanup, and live progress UI

- Add SyncFull trigger and configurable IMAP socket read timeout
  - Replace streaming UID FETCH with UID SEARCH ALL + batched fetch so per-message progress stays responsive and throttling servers can retry with reconnection
  - Finalize stale Running sessions on startup so interrupted syncs no longer show a phantom "syncing" state
  - Show a live syncing pill on the account row; add elapsed time, current folder, and slow-server warning styling in the dialog

web/src/locales/it.json

@@ -293,10 +293,14 @@
       },
       "message": "Messaggio",
       "session": {
+        "current_folder": "Cartella posta corrente",
+        "elapsed": "Tempo trascorso",
+        "last_update": "Ultimo aggiornamento",
         "started_at": "Ora di inizio",
         "status": "Stato",
-        "trigger": "Trigger"
+        "trigger": "Innesco"
       },
+      "syncing": "Sincronizzazione in corso",
       "tabs": {
         "active_session": "Sessione attiva",
         "errors": "Errori",