feat: implement full authentication system with middleware protection

- Install @supabase/ssr package for server-side auth
- Create middleware.ts for route protection (redirects to login if not authenticated)
- Fix login page admin check to verify specific user ID
- Add AUTH_SETUP.md with complete setup instructions
- Add setup-admin.sql for database configuration
- Logout button already exists in sidebar

admin-web/app/login/page.tsx

@@ -23,16 +23,19 @@ export default function LoginPage() {
     setError("");
 
     try {
-      const { error: authError } = await supabase.auth.signInWithPassword({
+      const { data: authData, error: authError } = await supabase.auth.signInWithPassword({
         email,
         password,
       });
 
       if (authError) throw authError;
+      if (!authData.user) throw new Error("Login failed");
 
+      // Check if the logged-in user is in admin_users table
       const { data: adminUser } = await supabase
         .from("admin_users")
         .select("*")
+        .eq("id", authData.user.id)
         .single();
 
       if (!adminUser) {