feat(titlebar): selectable window button styles + minimize toggle (#1083)

* feat(titlebar): selectable window button styles + minimize toggle

Custom title bar (Linux) gains a window-button style picker, mirroring
the seekbar style picker pattern. Six form-named styles: dots, dotsGlyph,
flat, pill, outline, glyph. All buttons now carry minimize/maximize/close
glyphs for clear, colour-blind-friendly iconography; dots reveal glyphs on
hover, dotsGlyph always shows them.

- New authStore state windowButtonStyle (default dots) + showMinimizeButton,
  with rehydrate validation falling back to dots on unknown values.
- WindowButtonPreview reuses the real .titlebar-btn classes for WYSIWYG tiles.
- Picker + minimize toggle render under the Custom title bar setting, gated
  on the toggle being on.
- Monochrome styles use --text-primary glyphs and stronger borders for
  contrast on dark themes.
- Dev-build grey marker scoped to the real title bar so previews show true
  colours.
- i18n keys in all 9 locales; setter and rehydrate tests.

* docs(changelog): window button styles (#1083)

src/components/TitleBar.tsx

@@ -1,11 +1,15 @@
 import React from 'react';
 import { getCurrentWindow } from '@tauri-apps/api/window';
+import { Minus, Square, X } from 'lucide-react';
 import { usePlayerStore } from '../store/playerStore';
+import { useAuthStore } from '../store/authStore';
 
 export default function TitleBar() {
   const win = getCurrentWindow();
   const currentTrack = usePlayerStore(s => s.currentTrack);
   const isPlaying = usePlayerStore(s => s.isPlaying);
+  const windowButtonStyle = useAuthStore(s => s.windowButtonStyle);
+  const showMinimizeButton = useAuthStore(s => s.showMinimizeButton);
 
   return (
     <div className="titlebar" data-tauri-drag-region>
@@ -20,28 +24,36 @@ export default function TitleBar() {
         )}
       </div>
 
-      <div className="titlebar-controls">
-        <button
-          className="titlebar-btn titlebar-btn-minimize"
-          onClick={() => win.minimize()}
-          data-tooltip="Minimize"
-          data-tooltip-pos="bottom"
-          aria-label="Minimize"
-        />
+      <div className="titlebar-controls" data-btnstyle={windowButtonStyle}>
+        {showMinimizeButton && (
+          <button
+            className="titlebar-btn titlebar-btn-minimize"
+            onClick={() => win.minimize()}
+            data-tooltip="Minimize"
+            data-tooltip-pos="bottom"
+            aria-label="Minimize"
+          >
+            <Minus size={10} strokeWidth={2.5} aria-hidden />
+          </button>
+        )}
         <button
           className="titlebar-btn titlebar-btn-maximize"
           onClick={() => win.toggleMaximize()}
           data-tooltip="Maximize"
           data-tooltip-pos="bottom"
           aria-label="Maximize"
-        />
+        >
+          <Square size={9} strokeWidth={2.5} aria-hidden />
+        </button>
         <button
           className="titlebar-btn titlebar-btn-close"
           onClick={() => win.close()}
           data-tooltip="Close"
           data-tooltip-pos="bottom"
           aria-label="Close"
-        />
+        >
+          <X size={10} strokeWidth={2.5} aria-hidden />
+        </button>
       </div>
     </div>
   );