fix(backend): sync push error handling + validation

- apply_push now uses PRAGMA table_info() to get valid column names per
  table and filters incoming data to only known columns, preventing
  "no such column" SQLite errors from frontend-only fields like oracle_id
- Wrap each operation in try/except so one bad op doesn't abort the
  whole batch; errors are returned in the conflicts list instead of 500
- Add server_default to all NOT NULL float/int columns so raw SQL
  INSERT OR REPLACE without those fields still succeeds
- Align DB models with frontend schema.js:
  - orders: add nr_comanda, client_nume, client_telefon, nr_auto,
    marca_denumire, model_denumire, created_by
  - order_lines: add norma_id, mecanic_id, ordine
  - vehicles: add serie_sasiu, client_cod_fiscal (keep vin, client_cui
    for REST API compat)
  - catalog_*: rename nume → denumire to match frontend schema
  - catalog_norme: align fields (cod, denumire, ore_normate)
  - invoices: add serie_factura, modalitate_plata, client_cod_fiscal,
    nr_auto, total_fara_tva, tva, total_general; keep total for compat
  - appointments: add client_nume, client_telefon, data_ora, durata_minute,
    status, order_id
  - mecanici: add user_id, prenume, activ
- Fix seed.py to use denumire= instead of nome= after catalog rename
- Add 3 new sync push tests covering order insert with frontend fields,
  unknown column filtering, and order_line with norma_id/mecanic_id/ordine

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

backend/app/db/models/appointment.py

@@ -1,4 +1,4 @@
-from sqlalchemy import String, Text
+from sqlalchemy import Integer, String, Text
 from sqlalchemy.orm import Mapped, mapped_column
 
 from app.db.base import Base, UUIDMixin, TenantMixin, TimestampMixin
@@ -6,6 +6,11 @@ from app.db.base import Base, UUIDMixin, TenantMixin, TimestampMixin
 
 class Appointment(Base, UUIDMixin, TenantMixin, TimestampMixin):
     __tablename__ = "appointments"
-    vehicle_id: Mapped[str] = mapped_column(String(36))
-    data: Mapped[str] = mapped_column(Text)
-    descriere: Mapped[str | None] = mapped_column(Text)
+    vehicle_id: Mapped[str | None] = mapped_column(String(36))
+    client_nume: Mapped[str | None] = mapped_column(String(200))
+    client_telefon: Mapped[str | None] = mapped_column(String(20))
+    data_ora: Mapped[str | None] = mapped_column(Text)
+    durata_minute: Mapped[int] = mapped_column(Integer, default=60, server_default="60")
+    observatii: Mapped[str | None] = mapped_column(Text)
+    status: Mapped[str] = mapped_column(String(20), default="PROGRAMAT", server_default="PROGRAMAT")
+    order_id: Mapped[str | None] = mapped_column(String(36))