[Archive Export] Implement archive export UI

Why are we doing this work

In this issue, we want to implement the user interface of the archive export functionality.

Relevant links

Design of the feature: #464638[Final_proposal_custom_date_range.png]

Implementation plan

• TBD

Verification steps

Locally verified because feature flag has not been enabled on any production environment yet.

1. Enable feature flag http://gdk.test:3000/rails/features/vulnerability_archival
2. Follow steps in guide https://handbook.gitlab.com/handbook/engineering/development/sec/security-risk-management/security-insights/vulnerability_archival_setup/#vulnerability-archive-generation-guide to create archived vulnerabilities
3. Go to the project > Secure > Security Configuration > Vulnerability Management
4. Verify there are vulnerabilities next to year
5. Click "Download all" and verify it downloads a .csv with all the vulnerabilities (also dated for full year of 2025)
6. Click expand arrow and click "Download" button in the month.
7. Verify it downloads a .csv with vulnerabilities of that month (filename is dated based on only that month)