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/main.py

@@ -5,6 +5,7 @@ from fastapi.middleware.cors import CORSMiddleware
 
 from app.auth.router import router as auth_router
 from app.client_portal.router import router as portal_router
+from app.clients.router import router as clients_router
 from app.config import settings
 from app.db.base import Base
 from app.db.session import engine
@@ -35,6 +36,7 @@ app.add_middleware(
 )
 app.include_router(auth_router, prefix="/api/auth")
 app.include_router(sync_router, prefix="/api/sync")
+app.include_router(clients_router, prefix="/api/clients")
 app.include_router(orders_router, prefix="/api/orders")
 app.include_router(vehicles_router, prefix="/api/vehicles")
 app.include_router(invoices_router, prefix="/api/invoices")