fix: fix right navigation overlapping buttons on AI providers page

Changes:
- Add right padding (80px) to content area to prevent ProviderNav from overlapping buttons
- Mobile responsive: reset right padding to 0 (navigation displays at bottom)

Modified files:
- src/pages/AiProvidersPage.module.scss (modified)

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

src/pages/AiProvidersPage.module.scss

@@ -73,8 +73,10 @@
   display: flex;
   flex-direction: column;
   gap: $spacing-xl;
+  padding-right: 80px; // 为右侧 ProviderNav 导航条预留空间
 
   @include mobile {
+    padding-right: 0; // 移动端导航在底部，不需要右侧预留
     padding-bottom: calc(72px + env(safe-area-inset-bottom));
   }
 }