feat(nav): tabs, list views and name searches are named in the address

Settings, Configuration and Users name their tab (stab/cfgtab/utab); a link's tab wins and a tab pre-selected
while its page is on screen now switches it. A playlist's sort, filters and grouping (plsort/plf/plgroup), the
Files sort (fsort, always written) and the name searches of Channels, Files, Playlists and Plex (cq/fq/plq/pq+pqf)
reopen from the address; the searches are written once the typing pauses.

frontend/src/lib/settingsTab.ts

@@ -1,8 +1,11 @@
 import { LS, setTabRaw } from "./storage";
 
 // The Settings page's tabs, and a helper to pre-select one before navigating there (a notice's link,
-// a return from Google). useTabPersistedState reads the key when the page mounts, and the page mounts
-// fresh on navigation. Kept out of SettingsPanel.tsx so a caller does not pull the page in with it.
+// a return from Google). useTabPersistedState reads the key when the page mounts, and the page on
+// screen hears it. Kept out of SettingsPanel.tsx so a caller does not pull the page in with it. The
+// address-bar key the page mirrors its tab to is here too, beside the other pages' keys.
+export const SETTINGS_TAB_KEY = "stab";
+
 export type SettingsTabId =
   | "appearance"
   | "notifications"