feat(ui): replace generic icons with official brand icons

- Add Claude and ChatGPT/Codex official brand SVG icons
- Create BrandIcons component with proper currentColor support
- Update AppSwitcher to use brand icons with Claude's official color (#D97757)
- Icons now dynamically change color based on active state
- Improve brand recognition and visual consistency

src/components/AppSwitcher.tsx

@@ -1,5 +1,5 @@
 import { AppType } from "../lib/tauri-api";
-import { Terminal, Code2 } from "lucide-react";
+import { ClaudeIcon, CodexIcon } from "./BrandIcons";
 
 interface AppSwitcherProps {
   activeApp: AppType;
@@ -23,8 +23,13 @@ export function AppSwitcher({ activeApp, onSwitch }: AppSwitcherProps) {
             : "text-gray-500 hover:text-gray-900 hover:bg-white/50 dark:text-gray-400 dark:hover:text-gray-100 dark:hover:bg-gray-800/60"
         }`}
       >
-        <Code2 size={16} />
-        <span>Claude Code</span>
+        <ClaudeIcon
+          size={16}
+          className={
+            activeApp === "claude" ? "text-[#D97757] dark:text-[#D97757]" : ""
+          }
+        />
+        <span>Claude</span>
       </button>
 
       <button
@@ -36,7 +41,7 @@ export function AppSwitcher({ activeApp, onSwitch }: AppSwitcherProps) {
             : "text-gray-500 hover:text-gray-900 hover:bg-white/50 dark:text-gray-400 dark:hover:text-gray-100 dark:hover:bg-gray-800/60"
         }`}
       >
-        <Terminal size={16} />
+        <CodexIcon size={16} />
         <span>Codex</span>
       </button>
     </div>