Add flexible Jira ticket creation — CVE/Vendor optional, source context tracking

Make CVE ID and Vendor optional when creating Jira tickets. Add source_context
field to track ticket origin (cve, archer, ivanti_queue, email, manual).

- Migration: drop NOT NULL on cve_id/vendor, add source_context column with CHECK
- Backend: update create/update/get endpoints for optional fields and source_context
- Frontend: update creation modal with optional labels and source context dropdown
- Add Create Jira Ticket action from Ivanti queue (pre-populates from finding)
- Add Create Jira Ticket action from Archer detail view (pre-populates from ticket)
- Add source context badge column, filter dropdown, and search to ticket list

backend/migrations/run-all.js

@@ -21,6 +21,7 @@ const POSTGRES_MIGRATIONS = [
     'add_vcl_vertical_metadata.js',
     'add_vcl_multi_vertical.js',
     'add_compliance_item_history.js',
+    'add_flexible_jira_ticket_creation.js',
 ];
 
 async function runAll() {