refactor(input): R10 S3b — one input recipe, ring focus everywhere

Unify text inputs onto the form.tsx inputCls look (surface bg, rounded-lg, 2px accent
RING focus), replacing the settings-family border-focus style app-wide:
- deleted 3 duplicate local `const inputCls` (KeyGate/SettingsPanel/SetupWizard) → import
  the shared one; a 4th (Welcome, py-2.5) kept local but re-styled to match.
- ~30 inline settings inputs: default full-size fields → inputCls; size variants (pager/
  table-filter/chat textarea/plex/glass-card) keep their width/radius/padding but swap
  bg-card→bg-surface and border-focus→ring-focus. glass-card/bg-transparent bgs left as-is.
- refreshed the form.tsx doc-comment (the old two-style split is gone).

The ring is the more visible / a11y-correct focus cue, matching R9's focus foundation.

frontend/src/components/Messages.tsx

@@ -13,6 +13,7 @@ import { openChat } from "../lib/chatDock";
 import * as e2ee from "../lib/e2ee";
 import Avatar from "./Avatar";
 import KeyGate from "./KeyGate";
+import { inputCls } from "./ui/form";
 import ChatThread from "./ChatThread";
 
 type View =
@@ -224,7 +225,7 @@ function Directory({ onPick, onBack }: { onPick: (u: MessageUser) => void; onBac
         value={filter}
         onChange={(e) => setFilter(e.target.value)}
         placeholder={t("messages.searchPeople")}
-        className="w-full bg-card border border-border rounded-xl px-3 py-2 text-sm outline-hidden focus:border-accent"
+        className={inputCls}
       />
       {q.isError && !q.data ? (
         <StateMessage tone="error" onRetry={() => q.refetch()}>