feat: persist worker-pause state across restarts

Worker pause states can optionally survive app restarts. A new toggle in
Settings saves the current pause map to settings/worker_pauses.json; on
startup lib.rs restores it before workers are spawned. Backend: new
snapshot/replace helpers in indexer.rs, persist functions in commands.rs
(get/set_worker_pauses_persist). Frontend: workerPausesPersist store
field, load/setWorkerPausesPersist actions, toggle in SettingsModal.

src/components/SettingsModal.tsx

@@ -228,6 +228,8 @@ export function SettingsModal() {
   const openAppDataFolder = useGalleryStore((state) => state.openAppDataFolder);
   const notificationsPaused = useGalleryStore((state) => state.notificationsPaused);
   const setNotificationsPaused = useGalleryStore((state) => state.setNotificationsPaused);
+  const workerPausesPersist = useGalleryStore((state) => state.workerPausesPersist);
+  const setWorkerPausesPersist = useGalleryStore((state) => state.setWorkerPausesPersist);
   const getDatabaseInfo = useGalleryStore((state) => state.getDatabaseInfo);
   const vacuumDatabase = useGalleryStore((state) => state.vacuumDatabase);
   const rebuildSemanticIndex = useGalleryStore((state) => state.rebuildSemanticIndex);
@@ -854,6 +856,19 @@ export function SettingsModal() {
                       <span className={`inline-block h-4 w-4 transform rounded-full bg-white shadow transition-transform ${notificationsPaused ? "translate-x-4" : "translate-x-0"}`} />
                     </button>
                   </SettingsItem>
+                  <SettingsItem
+                    label="Keep background pauses after restart"
+                    description="When enabled, folders you pause from the sidebar or background bar stay paused the next time Phokus opens."
+                  >
+                    <button
+                      role="switch"
+                      aria-checked={workerPausesPersist}
+                      className={`relative inline-flex h-5 w-9 shrink-0 cursor-pointer rounded-full border-2 border-transparent transition-colors focus:outline-none ${workerPausesPersist ? "bg-sky-500" : "bg-white/15"}`}
+                      onClick={() => setWorkerPausesPersist(!workerPausesPersist)}
+                    >
+                      <span className={`inline-block h-4 w-4 transform rounded-full bg-white shadow transition-transform ${workerPausesPersist ? "translate-x-4" : "translate-x-0"}`} />
+                    </button>
+                  </SettingsItem>
                 </SettingsGroup>
 
                 <SettingsGroup title="Maintenance">