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/SettingsPanel.tsx

@@ -9,7 +9,7 @@ import { LS, useAccountPersistedState } from "../lib/storage";
 import Avatar from "./Avatar";
 import { notify, type NotifSettings } from "../lib/notifications";
 import Tooltip from "./Tooltip";
-import { Section, SettingRow, Switch } from "./ui/form";
+import { inputCls, Section, SettingRow, Switch } from "./ui/form";
 import { type SaveState } from "./ui/DraftSaveBar";
 import { useConfirm } from "./ConfirmProvider";
 import { useWizard } from "./WizardProvider";
@@ -402,9 +402,6 @@ function SignInMethods({ me }: { me: Me }) {
     }
   };
 
-  const inputCls =
-    "w-full bg-card border border-border rounded-xl px-3 py-2 text-sm outline-hidden focus:border-accent";
-
   // Offer Google only when this instance has Google OAuth configured (or the account is already
   // linked — then we still show its "Connected" status even if the instance creds were removed).
   const showGoogle = me.google_enabled || me.has_google;