feat(qt): Offline settings 'Check now'

Hands out the connectivity actor's existing public request_recheck so
the row probes immediately instead of waiting for the next scheduled
check — the passthrough was the whole gap.

cc

crates/qbz-qt/qml/settings/OfflineSettings.qml

@@ -55,6 +55,18 @@ Column {
             onToggled: function (v) { QbzBridge.settingsBool("offline-mode-enabled", v) }
         }
     }
+    // Ask the connectivity actor for an immediate probe rather than waiting
+    // for its next scheduled one. Disabled under MANUAL offline (mode 2),
+    // where the answer is a user decision and not a network fact.
+    SettingRow {
+        label: QbzSession.tr("Check connection", QbzSession.trRev)
+        description: QbzSession.tr("Test the connection now instead of waiting for the next automatic check.", QbzSession.trRev)
+        SettingsButton {
+            text: QbzSession.tr("Check now", QbzSession.trRev)
+            enabled: QbzSession.offlineMode !== 2
+            onClicked: QbzBridge.settingsString("offline-recheck", "")
+        }
+    }
 
     SettingsSpacer { }
     SettingsDivider { }

crates/qbz-qt/src/offline_fwd.rs

@@ -57,6 +57,23 @@ pub fn start() {
     }
 }
 
+/// Settings > Offline "Check now": ask the actor for an immediate probe
+/// instead of waiting for its next scheduled one.
+///
+/// The passthrough is the whole gap this closes — `ConnectivityActor::
+/// request_recheck` has been public since the actor landed
+/// (`qbz-app/src/offline_mode/connectivity.rs:471`) and the reference exposes
+/// it the same way (`crates/qbz/src/offline_mode.rs:61-64`); this module just
+/// never handed out its private `OnceLock`.
+///
+/// A no-op before boot, which is when there is nothing to re-check anyway.
+pub fn request_recheck() {
+    match CONNECTIVITY.get() {
+        Some(actor) => actor.request_recheck(),
+        None => log::warn!("[qbz-qt] offline recheck ignored: connectivity actor not started"),
+    }
+}
+
 /// Mirror every engine status change into the bridge properties (the login
 /// affordances + the D2 recovery banner read them). Also seeds
 /// `hasPreviousSession` once; `enter_shell` refreshes it after a successful

crates/qbz-qt/src/settings_qt.rs

@@ -2483,6 +2483,10 @@ pub async fn settings_string(key: &str, value: String) {
         "plex-clear-cache" => library::plex_clear_cache().await,
         // --- Offline --------------------------------------------------------
         "lyrics-cache-clear" => offline::clear_lyrics_cache().await,
+        // Offline > "Check now": nudge the connectivity actor. The status it
+        // publishes flows back through offline_fwd's forwarder, so there is
+        // nothing to await and nothing to republish here.
+        "offline-recheck" => crate::offline_fwd::request_recheck(),
         // --- Developer ------------------------------------------------------
         "open-log-file" => devtools::open_log_file(),
         // The value is the include-auth gate ("with-auth" or empty) — see