feat(ui): upgrade @lobehub/icons to v5 and update agent icon colors

Upgrade @lobehub/icons from v4 to v5.3.0, adopt new icon components (ClaudeCode, Codex, GeminiCLI) with Color variants, and align fallback AGENT_COLORS with official brand colors.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

package.json

@@ -13,7 +13,7 @@
   },
   "dependencies": {
     "@base-ui/react": "^1.1.0",
-    "@lobehub/icons": "^4.11.0",
+    "@lobehub/icons": "^5.3.0",
     "@monaco-editor/react": "^4.7.0",
     "@radix-ui/react-use-controllable-state": "^1.2.2",
     "@streamdown/cjk": "^1.0.2",