feat(reference-auto) : add automatic reference generation for pieces

ModelType defines a formula with placeholders ({serie}{diametre}{type}).
ReferenceAutoGenerator resolves it from CustomFieldValues with trim+uppercase normalisation.
ReferenceAutoSubscriber (onFlush) recalculates on Piece/CFV insert/update/delete.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

config/services.yaml

@@ -64,3 +64,8 @@ when@test:
             autowire: true
             autoconfigure: true
             public: true
+
+        App\Service\ReferenceAutoGenerator:
+            autowire: true
+            autoconfigure: true
+            public: true