VSN-2829: Move vehicle age field from brand/model to individual vehicle
- Removes the
vehicleAgefield from the vehicle brand/model entity (form, schema, table, and types) - AddsvehicleAgeas an editable field directly on the vehicle form (optional, numeric, validated as non-negative integer) - Displays
vehicleAgeas a column in the vehicle list table with filter support - Removes the read-only "Ancienneté" derived display that was auto-populated from the brand/model selection