feat(infra): add repository implementations, mappers, FastAPI wiring, and technique indexes

backend/app/infrastructure/persistence/mappers/technique_mapper.py

@@ -0,0 +1,20 @@
+"""Technique ORM model <-> domain entity mapper."""
+
+from __future__ import annotations
+
+from app.domain.entities.technique import TechniqueEntity
+from app.domain.enums import TechniqueStatus
+
+
+class TechniqueMapper:
+    """Converts between SQLAlchemy Technique model and TechniqueEntity."""
+
+    @staticmethod
+    def to_entity(model: object) -> TechniqueEntity:
+        """Convert an ORM Technique model to a domain TechniqueEntity."""
+        return TechniqueEntity.from_orm(model)
+
+    @staticmethod
+    def to_model_updates(entity: TechniqueEntity, model: object) -> None:
+        """Apply entity changes back onto an existing ORM model."""
+        entity.apply_to(model)