Add conditional logging for development, improve token refresh logic, and remove outdated comments

- Wrap `console.log` calls in `if (process.env.NODE_ENV === 'development')` to prevent production logs in `forms/page.tsx`.
- Refactor token refresh logic by relying solely on the `refreshPromise` to avoid race conditions.
- Remove outdated `isRefreshing` flag, utilizing `refreshPromise` as the primary lock.
- Update comments in `IMPLEMENTATION_PLAN.md` to reflect the current progress and eliminate redundant sections.

frontend/src/app/dev/forms/page.tsx

@@ -79,7 +79,9 @@ export default function FormsPage() {
     setSubmitSuccess(false);
     // Simulate API call
     await new Promise((resolve) => setTimeout(resolve, 1500));
-    console.log('Login form data:', data);
+    if (process.env.NODE_ENV === 'development') {
+      console.log('Login form data:', data);
+    }
     setIsSubmitting(false);
     setSubmitSuccess(true);
   };
@@ -89,7 +91,9 @@ export default function FormsPage() {
     setSubmitSuccess(false);
     // Simulate API call
     await new Promise((resolve) => setTimeout(resolve, 1500));
-    console.log('Contact form data:', data);
+    if (process.env.NODE_ENV === 'development') {
+      console.log('Contact form data:', data);
+    }
     setIsSubmitting(false);
     setSubmitSuccess(true);
   };