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/Pager.tsx

@@ -87,7 +87,7 @@ export default function Pager({
               onBlur={commitPageInput}
               onKeyDown={(e) => e.key === "Enter" && commitPageInput()}
               aria-label={t("datatable.pager.pageLabel")}
-              className="w-14 bg-card border border-border rounded-md px-1.5 py-1 text-xs text-center tabular-nums outline-hidden focus:border-accent"
+              className="w-14 bg-surface border border-border rounded-md px-1.5 py-1 text-xs text-center tabular-nums focus:outline-hidden focus:ring-2 focus:ring-accent/40"
             />
             {t("datatable.pager.ofTotal", { total: totalPages })}
           </span>
@@ -110,7 +110,7 @@ export default function Pager({
               onSizeChange(Number(e.target.value));
               scrollListToTop();
             }}
-            className="bg-card border border-border rounded-md px-1.5 py-1 text-xs outline-hidden focus:border-accent"
+            className="bg-surface border border-border rounded-md px-1.5 py-1 text-xs focus:outline-hidden focus:ring-2 focus:ring-accent/40"
           >
             {pageSizeOptions.map((n) => (
               <option key={n} value={n}>