feat(design): the field family, the dropdown trigger, native controls, the no-raw-input lint rule (E28 S3c)

- ui/Input, Textarea, InnerInput + fieldClass (A4): the >= 3:1 edge, a 2px accent
  focus edge, the danger edge for invalid, md/sm/xs/heading rungs, 1rem and 44 on touch
- ui/SelectTrigger (A5): SortControl, FilterSelect, the view switcher and the date
  filter on one trigger, a pill in a toolbar, r8 in a form
- ui/NativeControls (A6): Checkbox, CheckRow, Slider, ColorInput
- every raw input swept (~100 sites); inputCls retired; local/input-primitive
- useReturnFocus: an in-place editor hands the focus back to its trigger on
  Enter/Escape (the playlist and Plex title renames, the priority number);
  the Plex playlist rename gains Escape and an accessible name
- back to top: a round 48 FAB (owner decision); DESIGN.md A2 and the log

frontend/src/components/ui/PriorityStepper.tsx

@@ -2,6 +2,7 @@ import { useCallback, useEffect, useRef, useState } from "react";
 import { Minus, Plus } from "lucide-react";
 import { useTranslation } from "react-i18next";
 import Tooltip from "./Tooltip";
+import { useReturnFocus } from "./useReturnFocus";
 
 type Size = "sm" | "md";
 
@@ -114,6 +115,7 @@ export function PriorityStepper({
     onPriority(delta);
   };
 
+  const editFocus = useReturnFocus(editing);
   const commitEdit = () => {
     const parsed = parseInt(draft, 10);
     if (!Number.isNaN(parsed) && parsed !== priority) onSet(parsed);
@@ -154,6 +156,7 @@ export function PriorityStepper({
           } ${cls.value}`}
         >
           <button
+            ref={editFocus.target}
             onClick={beginEdit}
             aria-label={t("common.priority.edit")}
             title={t("common.priority.edit")}
@@ -170,8 +173,13 @@ export function PriorityStepper({
               onChange={(e) => setDraft(e.target.value)}
               onBlur={commitEdit}
               onKeyDown={(e) => {
-                if (e.key === "Enter") commitEdit();
-                else if (e.key === "Escape") setEditing(false);
+                if (e.key === "Enter") {
+                  editFocus.arm();
+                  commitEdit();
+                } else if (e.key === "Escape") {
+                  editFocus.arm();
+                  setEditing(false);
+                }
               }}
               aria-label={hint}
               className="absolute inset-0 w-full h-full text-center font-medium tabular-nums text-accent bg-card outline-hidden [appearance:textfield] [&::-webkit-inner-spin-button]:appearance-none"