fix: 修复GitHub徽标hover颜色问题

1. 修改全局a标签hover颜色从primaryDark为primaryHover\n2. 为Logo组件添加明确的hover样式，避免受全局样式影响

Author: CC11001100

office-website/src/components/Header.tsx

@@ -39,6 +39,11 @@ const Logo = styled.a`
   span {
     margin-left: 0.5rem;
   }
+  
+  &:hover {
+    color: ${({ theme }) => theme.colors.primaryHover};
+    text-decoration: none;
+  }
 `;
 
 const NavLinks = styled.nav`

office-website/src/styles/GlobalStyles.ts

@@ -79,7 +79,7 @@ const GlobalStyles = createGlobalStyle`
     transition: ${({ theme }) => theme.transitions.fast};
     
     &:hover {
-      color: ${({ theme }) => theme.colors.primaryDark};
+      color: ${({ theme }) => theme.colors.primaryHover};
     }
   }