feat(survey-modal): add survey modal configuration to environment files

- Introduced a new environment variable VITE_ENABLE_SURVEY_MODAL to control the visibility of the survey modal.
- Updated .env.example to include the new variable with a default value of true.
- Modified SurveyPromptModal component to check the environment variable before displaying the modal, enhancing user experience by allowing toggling of the feature.

worklenz-frontend/src/components/survey/SurveyPromptModal.tsx

@@ -30,6 +30,11 @@ export const SurveyPromptModal: React.FC<SurveyPromptModalProps> = ({ forceShow
   const isDarkMode = themeMode === 'dark';
 
   useEffect(() => {
+    // Check if survey modal is disabled via environment variable
+    if (import.meta.env.VITE_ENABLE_SURVEY_MODAL !== 'true' && !forceShow) {
+      return; // Don't show modal if disabled in environment
+    }
+
     // Check if survey was skipped recently (within 7 days)
     const skippedAt = localStorage.getItem('survey_skipped_at');
     if (!forceShow && skippedAt) {