feat(phase-37): timer pause/resume + professional reporting engine

Pause/Resume timer:
- Add paused_at, red_paused_seconds, blue_paused_seconds fields to Test model
- Add pause_timer/resume_timer workflow functions with accumulated pause tracking
- Auto-resume on phase submit; subtract paused time from worklog duration
- Add POST /tests/{id}/pause-timer and resume-timer endpoints
- Update LiveTimer component with pause/resume button and paused visual state
- Wire pause/resume mutations through TestDetailPage and TestDetailHeader

Professional Reporting Engine - Fase 2:
- Add ReportEngine service with Jinja2 HTML rendering, WeasyPrint PDF, and docxtpl DOCX
- Add corporate CSS stylesheet with cover page, data tables, stats grid, findings
- Create purple_campaign, coverage_report, and executive_summary HTML templates
- Add report_generation_service collecting domain data for each report type
- Add professional_reports router: GET /reports/generate/purple-campaign/{id}, coverage-summary, executive-summary
- Add analytics router with flat JSON endpoints for PowerBI: /coverage, /tests, /trends, /operators
- Add advanced_metrics router: /coverage-by-tactic, /never-tested, /avg-validation-time, /detection-rate-trend
- Add weasyprint and docxtpl to requirements.txt
- Add REPORT_TEMPLATES_DIR, REPORT_OUTPUT_DIR, COMPANY_NAME, COMPANY_LOGO_PATH to config

backend/app/models/test.py

@@ -52,6 +52,9 @@ class Test(Base):
     # ── Phase timing fields (for automatic Tempo worklogs) ──────────
     red_started_at = Column(DateTime, nullable=True)
     blue_started_at = Column(DateTime, nullable=True)
+    paused_at = Column(DateTime, nullable=True)
+    red_paused_seconds = Column(Integer, default=0)
+    blue_paused_seconds = Column(Integer, default=0)
 
     # ── Remediation fields ───────────────────────────────────────────
     remediation_steps = Column(Text, nullable=True)