feat: optimize logo display (#6267)

* feat(VbenAvatar): add fit property to VbenAvatar component

* feat(VbenLogo): add fit property to VbenLogo component

* feat(VbenLogo): add logo fit preference configuration

- Add preferences.logo.fit setting for logo display control
- Include corresponding documentation for the new preference

* feat(preferences): add default value for logo.fit preference

- Set default configuration for logo fit behavior
- Ensures consistent logo display across applications

* test(preferences): update configuration snapshots

---------

Co-authored-by: wyc001122 <wangyongchao@testor.com.cn>

packages/@core/preferences/__tests__/__snapshots__/config.test.ts.snap

@@ -61,6 +61,7 @@ exports[`defaultPreferences immutability test > should not modify the config obj
   },
   "logo": {
     "enable": true,
+    "fit": "contain",
     "source": "https://unpkg.com/@vbenjs/static-source@0.1.7/source/logo-v1.webp",
   },
   "navigation": {