fix(jira): expose non-admin jira-config, drop security-test label; catalog paging

GET /system/jira-config was admin-only, so non-admin users hit a 403
and the frontend silently fell back to a hardcoded jira.atlassian.com
base URL when building /browse/{key} links. Opened it to any
authenticated user (still no secrets returned).

Also drops the redundant 'security-test' Jira label, and adds a
page-size selector (10/25/50/100) and a 'no existing test yet' filter
to the Test Catalog.

backend/app/services/jira_service.py

@@ -700,7 +700,7 @@ def auto_create_test_issue(
 
         poc = test.procedure_text or "N/A"
         severity = _technique_severity(technique).capitalize()
-        labels = ["aegis", "security-test", mitre_id.replace(".", "-")]
+        labels = ["aegis", mitre_id.replace(".", "-")]
         if test.platform:
             # Jira labels can't contain whitespace — normalize to kebab-case.
             labels.append(re.sub(r"[^a-z0-9_-]+", "-", test.platform.lower()).strip("-"))