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/db/models/vehicle.py

@@ -7,6 +7,7 @@ from app.db.base import Base, UUIDMixin, TenantMixin, TimestampMixin
 class Vehicle(Base, UUIDMixin, TenantMixin, TimestampMixin):
     __tablename__ = "vehicles"
     nr_inmatriculare: Mapped[str] = mapped_column(String(20))
+    client_id: Mapped[str | None] = mapped_column(String(36))
     marca_id: Mapped[str | None] = mapped_column(String(36))
     model_id: Mapped[str | None] = mapped_column(String(36))
     an_fabricatie: Mapped[int | None] = mapped_column(Integer)