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/Feed.tsx

@@ -410,7 +410,7 @@ export default function Feed({
                 value={ytCount}
                 onChange={(e) => setYtCount(Number(e.target.value))}
                 title={t("feed.yt.showHint")}
-                className="bg-card border border-border rounded-lg px-2 py-1 text-xs outline-hidden focus:border-accent"
+                className="bg-surface border border-border rounded-lg px-2 py-1 text-xs focus:outline-hidden focus:ring-2 focus:ring-accent/40"
               >
                 {[20, 40, 60, 100].map((n) => (
                   <option key={n} value={n}>
@@ -603,7 +603,7 @@ export default function Feed({
                   })
                 }
                 title={t("feed.source.tip")}
-                className="bg-card border border-border rounded-lg px-2 py-1 text-xs outline-hidden focus:border-accent"
+                className="bg-surface border border-border rounded-lg px-2 py-1 text-xs focus:outline-hidden focus:ring-2 focus:ring-accent/40"
               >
                 <option value="organic">{t("feed.source.organic")}</option>
                 <option value="all">{t("feed.source.all")}</option>
@@ -637,7 +637,7 @@ export default function Feed({
               });
             }}
             aria-label={t("feed.sortLabel")}
-            className="bg-card border border-border rounded-lg px-2 py-1.5 text-sm outline-hidden focus:border-accent"
+            className="bg-surface border border-border rounded-lg px-2 py-1.5 text-sm focus:outline-hidden focus:ring-2 focus:ring-accent/40"
           >
             {/* Relevance only ranks meaningfully when there's a search term — offer it then. */}
             {(filters.q.trim() ? (["relevance", ...sortKeys] as SortKey[]) : sortKeys).map((k) => (