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/services/report_engine.py

@@ -0,0 +1,93 @@
+"""Report engine — renders Jinja2 HTML templates to PDF, DOCX, and HTML.
+
+Uses WeasyPrint for PDF generation and docxtpl for DOCX.
+"""
+
+import os
+import uuid
+import logging
+from datetime import datetime
+
+from jinja2 import Environment, FileSystemLoader
+
+from app.config import settings
+
+logger = logging.getLogger(__name__)
+
+
+class ReportEngine:
+    """Template-based report generator supporting PDF, DOCX, and HTML output."""
+
+    def __init__(self) -> None:
+        self.jinja_env = Environment(
+            loader=FileSystemLoader(settings.REPORT_TEMPLATES_DIR),
+            autoescape=True,
+        )
+        os.makedirs(settings.REPORT_OUTPUT_DIR, exist_ok=True)
+
+    def render_html(self, template_name: str, context: dict) -> str:
+        """Render a Jinja2 template to an HTML string."""
+        template = self.jinja_env.get_template(f"{template_name}.html")
+        context.setdefault("company_name", settings.COMPANY_NAME)
+        context.setdefault("generated_at", datetime.utcnow().strftime("%B %d, %Y %H:%M UTC"))
+        return template.render(context)
+
+    def generate_pdf(self, template_name: str, context: dict) -> str:
+        """Render HTML and convert to PDF with WeasyPrint."""
+        from weasyprint import HTML, CSS
+
+        html_content = self.render_html(template_name, context)
+        css_path = os.path.join(settings.REPORT_TEMPLATES_DIR, "styles", "report.css")
+        output_path = os.path.join(
+            settings.REPORT_OUTPUT_DIR,
+            f"{template_name}_{uuid.uuid4().hex[:8]}.pdf",
+        )
+
+        stylesheets = []
+        if os.path.exists(css_path):
+            stylesheets.append(CSS(filename=css_path))
+
+        HTML(
+            string=html_content,
+            base_url=settings.REPORT_TEMPLATES_DIR,
+        ).write_pdf(output_path, stylesheets=stylesheets)
+
+        logger.info("PDF generated: %s", output_path)
+        return output_path
+
+    def generate_docx(self, template_name: str, context: dict) -> str:
+        """Render a .docx template with docxtpl."""
+        from docxtpl import DocxTemplate
+
+        template_path = os.path.join(
+            settings.REPORT_TEMPLATES_DIR, f"{template_name}.docx"
+        )
+        output_path = os.path.join(
+            settings.REPORT_OUTPUT_DIR,
+            f"{template_name}_{uuid.uuid4().hex[:8]}.docx",
+        )
+
+        doc = DocxTemplate(template_path)
+        context.setdefault("company_name", settings.COMPANY_NAME)
+        context.setdefault("generated_at", datetime.utcnow().strftime("%B %d, %Y"))
+        doc.render(context)
+        doc.save(output_path)
+
+        logger.info("DOCX generated: %s", output_path)
+        return output_path
+
+    def generate_html_file(self, template_name: str, context: dict) -> str:
+        """Render and save a standalone HTML report."""
+        html_content = self.render_html(template_name, context)
+        output_path = os.path.join(
+            settings.REPORT_OUTPUT_DIR,
+            f"{template_name}_{uuid.uuid4().hex[:8]}.html",
+        )
+        with open(output_path, "w", encoding="utf-8") as f:
+            f.write(html_content)
+
+        logger.info("HTML report generated: %s", output_path)
+        return output_path
+
+
+report_engine = ReportEngine()