refactor(quick-settings): migrate panel to typed feature-based modules

Refactor QuickSettingsPanel from a single JSX component into a modular TypeScript feature structure while preserving behavior and translations.

Highlights:
- Replace legacy src/components/QuickSettingsPanel.jsx with a typed entrypoint (src/components/QuickSettingsPanel.tsx).
- Introduce src/components/quick-settings-panel/ with clear separation of concerns:
  - view/: panel shell, header, handle, section wrappers, toggle rows, and content sections.
  - hooks/: drag interactions and whisper mode persistence.
  - constants.ts and types.ts for shared config and strict local typing.
- Move drag logic into useQuickSettingsDrag with explicit touch/mouse handling, drag threshold detection, click suppression after drag, position clamping, and localStorage persistence.
- Keep user-visible behavior intact:
  - same open/close panel interactions.
  - same mobile/desktop drag behavior and persisted handle position.
  - same quick preference toggles and wiring to useUiPreferences.
  - same hidden whisper section behavior and localStorage/event updates.
- Improve readability and maintainability by extracting repetitive setting rows and section scaffolding into reusable components.
- Add focused comments around non-obvious behavior (drag click suppression, touch scroll lock, hidden whisper section intent).
- Keep files small and reviewable (all new/changed files are under 300 lines).

Validation:
- npm run typecheck
- npm run build

src/components/quick-settings-panel/view/QuickSettingsSection.tsx

@@ -0,0 +1,22 @@
+import type { ReactNode } from 'react';
+
+type QuickSettingsSectionProps = {
+  title: string;
+  children: ReactNode;
+  className?: string;
+};
+
+export default function QuickSettingsSection({
+  title,
+  children,
+  className = '',
+}: QuickSettingsSectionProps) {
+  return (
+    <div className={`space-y-2 ${className}`}>
+      <h4 className="text-xs font-semibold uppercase tracking-wider text-gray-500 dark:text-gray-400 mb-2">
+        {title}
+      </h4>
+      {children}
+    </div>
+  );
+}