Fix React Strict Mode double-call issue in Google Calendar integration

- Add state-based lock (isTestRunning) to prevent duplicate API calls
- Update error handling in edge function for body consumption
- Add OAuth2 token generation helper tool (get-google-token-local.html)

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

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

src/components/admin/settings/IntegrasiTab.tsx

@@ -52,6 +52,7 @@ export function IntegrasiTab() {
   const [saving, setSaving] = useState(false);
   const [testEmail, setTestEmail] = useState('');
   const [sendingTest, setSendingTest] = useState(false);
+  const [isTestRunning, setIsTestRunning] = useState(false);
 
   useEffect(() => {
     fetchSettings();
@@ -380,9 +381,11 @@ export function IntegrasiTab() {
                 return;
               }
 
-              // Prevent multiple simultaneous clicks
-              const btn = document.activeElement as HTMLButtonElement;
-              if (btn) btn.disabled = true;
+              if (isTestRunning) {
+                return; // Prevent React Strict Mode double-call
+              }
+
+              setIsTestRunning(true);
 
               try {
                 const { data, error } = await supabase.functions.invoke('create-google-meet-event', {
@@ -406,9 +409,10 @@ export function IntegrasiTab() {
               } catch (err: any) {
                 toast({ title: "Error", description: err.message, variant: "destructive" });
               } finally {
-                if (btn) btn.disabled = false;
+                setIsTestRunning(false);
               }
             }}
+            disabled={isTestRunning}
             className="w-full border-2"
           >
             Test Google Calendar Connection