feat(desktop): add minimum window size constraints

Set minWidth: 500 and minHeight: 520 to prevent UI breakage.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/desktop/src/main/index.ts

@@ -73,6 +73,8 @@ function createWindow() {
   win = new BrowserWindow({
     width: 1200,
     height: 800,
+    minWidth: 500,
+    minHeight: 520,
     titleBarStyle: 'hiddenInset',
     trafficLightPosition: { x: 16, y: 17 },  // Vertically centered in 48px header
     webPreferences: {