refactor(frontend): Begin modularizing work-report-calendar

Initiated the process of refactoring the monolithic `work-report-calendar.js` file as outlined in the Phase 2 frontend modernization plan.

- Created `CalendarAPI.js` to encapsulate all API calls related to the calendar, centralizing data fetching logic.
- Created `CalendarState.js` to manage the component's state, removing global variables from the main script.
- Refactored `work-report-calendar.js` to use the new state and API modules.
- Refactored `manage-project.js` to use the existing global API helpers, providing a consistent example for API usage.

web-ui/pages/common/daily-work-report-viewer.html

@@ -337,6 +337,8 @@
     <script src="/js/api-config.js?v=13"></script>
     <script src="/js/auth-check.js?v=13"></script>
     <script src="/js/load-navbar.js?v=4"></script>
+    <script src="/js/modules/calendar/CalendarState.js?v=1"></script>
+    <script src="/js/modules/calendar/CalendarAPI.js?v=1"></script>
     <script src="/js/work-report-calendar.js?v=41"></script>
 </body>
 </html>