fix: increase desktop macOS icon footprint

The macOS icon rendered smaller than neighboring Dock icons because the
source artwork left a 120px margin on the 1024px canvas. Scale the macOS
source to the expected 96px margin and regenerate the Tauri icon set so
bundled app assets stay in sync.

Constraint: macOS source artwork should fit a 1024px canvas with 96px icon spacing
Rejected: Adjust only the Dock screenshot or public preview asset | packaged icon.icns would remain undersized
Confidence: high
Scope-risk: narrow
Directive: Regenerate desktop/src-tauri/icons when changing app-icon-macos.svg
Tested: cd desktop && bun run lint
Tested: icon.icns expanded 1024px image reports 96px margins on all sides
Not-tested: Full macOS app rebuild

desktop/src-tauri/app-icon-macos.svg

@@ -27,6 +27,7 @@
     </linearGradient>
   </defs>
 
+  <g transform="translate(512 512) scale(1.0612244898) translate(-512 -512)">
   <rect x="120" y="120" width="784" height="784" rx="180" fill="url(#panel)"/>
   <rect x="124" y="124" width="776" height="776" rx="176" stroke="url(#panelGlow)" stroke-width="8"/>
   <path d="M236 260C324 190 464 170 612 206" stroke="#5C2E1D" stroke-width="18" stroke-linecap="round" opacity="0.58"/>
@@ -39,4 +40,5 @@
   <g filter="url(#sparkGlow)">
     <path d="M592 334L608.8 385.2L660 402L608.8 418.8L592 470L575.2 418.8L524 402L575.2 385.2L592 334Z" fill="url(#spark)"/>
   </g>
+  </g>
 </svg>