Refactor global styles and enhance MITM functionality

- Updated global CSS to implement a new brand color palette and improve light/dark theme consistency.
- Enhanced the MitmServerCard component to provide clearer user feedback regarding admin privileges.
- Filtered LLM combos in the CombosPage to ensure only relevant data is displayed.
- Improved APIPageClient layout for better usability and visual consistency.
- Added functionality to save and load DNS tool states in the MITM manager.
- Updated OAuth configuration URLs for Qwen to reflect the new endpoint structure.
- Refined tunnel management logic to improve reliability and user experience.

src/shared/components/layouts/DashboardLayout.js

@@ -91,7 +91,9 @@ export default function DashboardLayout({ children }) {
       </div>
 
       {/* Main content */}
-      <main className="flex flex-col flex-1 h-full min-w-0 relative transition-colors duration-300">
+      <main className="flex flex-col flex-1 h-full min-w-0 relative transition-colors duration-300 isolate">
+        {/* Faint grid background */}
+        <div className="landing-grid absolute inset-0 pointer-events-none -z-10" aria-hidden="true" />
         <Header key={pathname} onMenuClick={() => setSidebarOpen(true)} />
         <div className={`flex-1 overflow-y-auto custom-scrollbar ${pathname === "/dashboard/basic-chat" ? "" : "p-6 lg:p-10"} ${pathname === "/dashboard/basic-chat" ? "flex flex-col overflow-hidden" : ""}`}>
           <div className={`${pathname === "/dashboard/basic-chat" ? "flex-1 w-full h-full flex flex-col" : "max-w-7xl mx-auto"}`}>{children}</div>