feat: FASE 6.5 - Report PDF (WeasyPrint + Kaleido)

Add PDF report generation for Metrologist dashboard with SPC and
measurement reports including SVG charts, capability indices, and
company logo embedding.

New files:
- server/services/report_service.py (Jinja2 + Plotly/Kaleido + WeasyPrint)
- server/routers/reports.py (2 GET endpoints with auth)
- server/templates/reports/ (base, spc, measurement HTML templates)

Modified:
- server/main.py (register reports router)
- client dashboard (download buttons + proxy routes)
- i18n strings IT/EN

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/main.py

@@ -15,6 +15,7 @@ from routers.tasks import router as tasks_router
 from routers.measurements import router as measurements_router
 from routers.files import router as files_router
 from routers.settings import router as settings_router
+from routers.reports import router as reports_router
 from routers.statistics import router as statistics_router
 
 
@@ -60,6 +61,7 @@ app.include_router(measurements_router)
 app.include_router(files_router)
 app.include_router(settings_router)
 app.include_router(statistics_router)
+app.include_router(reports_router)
 
 
 @app.get("/api/health")