[#664] feat(feedback): implement secure feedback download functionality

[wayangalihpratama]

Description

This PR implements the 'Download Feedback' functionality for administrators.

Key Changes:

• Backend:
  • Refactored get_feedback_for_export in backend/db/crud_feedback.py to support multi-ISCO filtering.
  • Created generate_feedback_export utility in backend/util/sheets.py using pandas and xlsxwriter.
  • Added GET /api/feedback/download route in backend/routes/feedback.py with strict ISCO-based access control.
  • Added GET /api/isco_type/mine in backend/routes/isco_type.py to provide user-specific ISCO context.
• Frontend:
  • Added 'Download Feedback' task to the Admin dashboard in Admin.jsx.
  • Created a dedicated Download Feedback page (DownloadFeedback.jsx) with ISCO and Monitoring Round selectors.
  • Implemented dynamic ISCO filtering based on user permissions.
  • Styled the new page to match the project's admin interface in style.scss.
• Security:
  • Enforced role-based access control (Secretariat vs. Member Admin) via verify_admin middleware.
  • Validated ISCO permissions on both frontend and backend.
• Testing:
  • Added comprehensive backend tests in backend/tests/test_111_feedback_download.py (all 185 tests in suite passing).
  • Handled date-suffixed filename verification (feedback_export_YYYYMMDD.xlsx).

Verification:

• All 185 backend tests passed.
• Frontend linting passed.

Closes #664

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• To see the specific tasks where the Asana app for GitHub is being used, see below:
  • https://app.asana.com/0/0/1213758325273735

[coveralls]

coverage: 86.285% (+0.1%) from 86.185%
when pulling b61b0d6 on feature/664-add-a-feedback-download-functionality
into ab73c38 on develop.