feat(prospecting): implement security audit pipeline (Workstream 2A)

Complete security audit integration into the enrichment pipeline:

Backend:
- SecurityAuditService with 7 passive checks: HTTPS, SSL cert, security
  headers, exposed files, cookies, server info, technology detection
- Constants file with SECURITY_HEADERS, EXPOSED_PATHS, SEVERITY_SCORES
- SecurityAuditResponse schema with JSON field validators + aliases
- Endpoints: POST /security-audit/{id}, POST /security-audit/batch
- Added to full_enrichment pipeline (Step 5, before scoring)
- get_pending_security_audit() query in prospect_service

Frontend:
- Security tab on prospect detail page with grade badge (A+ to F),
  score/100, severity counts, HTTPS/SSL status, missing headers,
  exposed files, technologies, and full findings list
- "Run Security Audit" button with loading state
- "Security Audit" batch button on scan-jobs page

Tested on batirenovation-strasbourg.fr: Grade D (50/100), 11 issues
found (missing headers, exposed wp-login, server version disclosure).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/modules/prospecting/templates/prospecting/admin/scan-jobs.html

@@ -34,6 +34,11 @@
             <span x-html="$icon('mail', 'w-4 h-4 mr-2')"></span>
             Contact Scrape
         </button>
+        <button type="button" @click="startBatchJob('security_audit')"
+                class="inline-flex items-center px-4 py-2 text-sm font-medium leading-5 text-white transition-colors duration-150 bg-yellow-600 border border-transparent rounded-lg hover:bg-yellow-700 focus:outline-none">
+            <span x-html="$icon('shield-check', 'w-4 h-4 mr-2')"></span>
+            Security Audit
+        </button>
         <button type="button" @click="startBatchJob('score_compute')"
                 class="inline-flex items-center px-4 py-2 text-sm font-medium leading-5 text-white transition-colors duration-150 bg-red-600 border border-transparent rounded-lg hover:bg-red-700 focus:outline-none">
             <span x-html="$icon('cursor-click', 'w-4 h-4 mr-2')"></span>