feat: add clients nomenclator, order edit/delete/devalidate, invoice types, dashboard redesign

- New clients table with PF/PJ support, fiscal data (CUI, IBAN, eFactura fields)
- Full CRUD API for clients with search, sync integration
- Order lifecycle: edit header (DRAFT), devalidate (VALIDAT→DRAFT), delete order/invoice
- Invoice types: FACTURA (B2B) vs BON_FISCAL (B2C) with different nr formats
- OrderCreateView redesigned as multi-step flow (client→vehicle→details)
- Autocomplete from catalog_norme/catalog_preturi in OrderLineForm
- Dashboard now combines stats + full orders table with filter tabs and search
- ClientPicker and VehiclePicker with inline creation capability
- Frontend schema aligned with backend (missing columns causing sync errors)
- Mobile responsive fixes for OrderDetailView buttons

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

backend/app/invoices/router.py

@@ -1,3 +1,5 @@
+from datetime import UTC, datetime
+
 from fastapi import APIRouter, Depends, HTTPException
 from fastapi.responses import Response
 from sqlalchemy import select
@@ -109,3 +111,39 @@ async def get_invoice_pdf(
             "Content-Disposition": f'inline; filename="factura-{invoice.nr_factura}.pdf"'
         },
     )
+
+
+@router.delete("/{invoice_id}")
+async def delete_invoice(
+    invoice_id: str,
+    tenant_id: str = Depends(get_tenant_id),
+    db: AsyncSession = Depends(get_db),
+):
+    r = await db.execute(
+        select(Invoice).where(
+            Invoice.id == invoice_id, Invoice.tenant_id == tenant_id
+        )
+    )
+    invoice = r.scalar_one_or_none()
+    if not invoice:
+        raise HTTPException(status_code=404, detail="Invoice not found")
+
+    order_id = invoice.order_id
+
+    # Delete the invoice
+    await db.delete(invoice)
+
+    # Revert the associated order status back to VALIDAT
+    if order_id:
+        r = await db.execute(
+            select(Order).where(
+                Order.id == order_id, Order.tenant_id == tenant_id
+            )
+        )
+        order = r.scalar_one_or_none()
+        if order:
+            order.status = "VALIDAT"
+            order.updated_at = datetime.now(UTC).isoformat()
+
+    await db.commit()
+    return {"ok": True}