feat(backend): PDF deviz + portal client + SMS + invoice service

- PDF generation with WeasyPrint: deviz and factura templates (A4, branding)
- GET /orders/{id}/pdf/deviz returns PDF with order lines and totals
- Client portal (public, no auth): GET /p/{token}, POST /p/{token}/accept|reject
- SMS service (SMSAPI.ro) - skips in dev when no token configured
- Invoice service: create from validated order, auto-number (F-YYYY-NNNN)
- GET /invoices/{id}/pdf returns factura PDF
- Order status_client field for client accept/reject tracking
- Alembic migration for status_client
- 19 passing tests (auth + sync + orders + pdf + portal + invoices)

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

backend/app/pdf/service.py

@@ -0,0 +1,30 @@
+from pathlib import Path
+
+from jinja2 import Environment, FileSystemLoader
+from weasyprint import HTML
+
+TEMPLATES = Path(__file__).parent / "templates"
+
+
+def generate_deviz(order: dict, lines: list, tenant: dict) -> bytes:
+    env = Environment(loader=FileSystemLoader(str(TEMPLATES)))
+    html = env.get_template("deviz.html").render(
+        order=order,
+        tenant=tenant,
+        manopera=[l for l in lines if l.get("tip") == "manopera"],
+        materiale=[l for l in lines if l.get("tip") == "material"],
+    )
+    return HTML(string=html).write_pdf()
+
+
+def generate_factura(
+    invoice: dict, order: dict, lines: list, tenant: dict
+) -> bytes:
+    env = Environment(loader=FileSystemLoader(str(TEMPLATES)))
+    html = env.get_template("factura.html").render(
+        invoice=invoice,
+        order=order,
+        tenant=tenant,
+        lines=lines,
+    )
+    return HTML(string=html).write_pdf()