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/invoices/service.py

@@ -0,0 +1,49 @@
+from datetime import UTC, datetime
+
+from sqlalchemy import select, text
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.db.base import uuid7
+from app.db.models.invoice import Invoice
+from app.db.models.order import Order
+
+
+async def create_invoice(
+    db: AsyncSession, tenant_id: str, order_id: str
+) -> Invoice:
+    r = await db.execute(
+        select(Order).where(Order.id == order_id, Order.tenant_id == tenant_id)
+    )
+    order = r.scalar_one_or_none()
+    if not order:
+        raise ValueError("Order not found")
+    if order.status != "VALIDAT":
+        raise ValueError("Order must be VALIDAT to create invoice")
+
+    # Generate next invoice number for this tenant
+    r = await db.execute(
+        text(
+            "SELECT COUNT(*) as cnt FROM invoices WHERE tenant_id = :tid"
+        ),
+        {"tid": tenant_id},
+    )
+    count = r.scalar() + 1
+    now = datetime.now(UTC)
+    nr_factura = f"F-{now.year}-{count:04d}"
+
+    invoice = Invoice(
+        id=uuid7(),
+        tenant_id=tenant_id,
+        order_id=order_id,
+        nr_factura=nr_factura,
+        data_factura=now.isoformat().split("T")[0],
+        total=order.total_general,
+    )
+    db.add(invoice)
+
+    # Update order status to FACTURAT
+    order.status = "FACTURAT"
+    order.updated_at = now.isoformat()
+    await db.commit()
+    await db.refresh(invoice)
+    return invoice