feat: v0.2.0 - add system tray, clean up unused role field

- Replace text '+' icon with centered SVG plus icon for the add-provider button
- Add system tray: minimize-to-tray and quit-from-tray menu (minimize hides window, close exits app)
- Remove unused model role field (no functional effect, only stored/displayed)
- Fix multiple providers showing as active in Kimi Code mode: only the default_model's provider is marked active
- Copy /reload to clipboard after provider switch as a convenience hint
- Bump version to 0.2.0

index.html

@@ -2,9 +2,9 @@
 <html lang="zh-CN">
   <head>
     <meta charset="UTF-8" />
-    <link rel="icon" type="image/svg+xml" href="/pi.svg" />
+    <link rel="icon" type="image/svg+xml" href="/kimi.svg" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
-    <title>Pi Switch</title>
+    <title>Kimi Switch</title>
   </head>
   <body>
     <div id="root"></div>