fix: Remove client-side auth redirects causing dashboard flashing

- Removed checkAuth() function and redirects from dashboard.astro
- Removed checkAuth() function and redirects from events/new.astro
- Updated to use Astro.cookies for better SSR compatibility
- Client-side code now focuses on data loading, not authentication
- Server-side unified auth system handles all protection

🤖 Generated with [Claude Code](https://claude.ai/code)

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

src/pages/dashboard.astro

@@ -351,26 +351,23 @@ if (!auth) {
     }, 8000);
   }
 
-  // Check authentication and redirect immediately if no session
-  async function checkAuth() {
-    const { data: { session } } = await supabase.auth.getSession();
-    if (!session) {
-      // No session found, redirecting to login
-      window.location.href = '/login';
-      return null;
-    }
-    return session;
-  }
+  // Note: Authentication is now handled server-side by unified auth system
 
   // Load events
   async function loadEvents() {
     try {
-      // Check if user has organization_id or is admin
+      // Get current user (auth already verified server-side)
       const { data: { user } } = await supabase.auth.getUser();
       
       if (!user) {
-        // User is null, redirecting to login
-        window.location.href = '/login';
+        // This shouldn't happen due to server-side auth, but handle gracefully
+        console.error('No user found despite server-side auth');
+        loading.innerHTML = `
+          <div class="rounded-xl p-6 max-w-md mx-auto" style="background: var(--error-bg); border: 1px solid var(--error-border);">
+            <p class="font-medium" style="color: var(--error-color);">Session error</p>
+            <p class="text-sm mt-2" style="color: var(--error-color); opacity: 0.8;">Please refresh the page</p>
+          </div>
+        `;
         return;
       }
       
@@ -830,9 +827,6 @@ if (!auth) {
   // Handle onboarding success on page load
   handleOnboardingSuccess();
   
-  checkAuth().then(session => {
-    if (session) {
-      loadEvents();
-    }
-  });
+  // Load events directly (auth already verified server-side)
+  loadEvents();
 </script>