chore: move pytest fixture plugin + update fixture module structure

src/fastapi_toolsets/fixtures/enum.py

@@ -0,0 +1,30 @@
+from enum import Enum
+
+
+class LoadStrategy(str, Enum):
+    """Strategy for loading fixtures into the database."""
+
+    INSERT = "insert"
+    """Insert new records. Fails if record already exists."""
+
+    MERGE = "merge"
+    """Insert or update based on primary key (SQLAlchemy merge)."""
+
+    SKIP_EXISTING = "skip_existing"
+    """Insert only if record doesn't exist (based on primary key)."""
+
+
+class Context(str, Enum):
+    """Predefined fixture contexts."""
+
+    BASE = "base"
+    """Base fixtures loaded in all environments."""
+
+    PRODUCTION = "production"
+    """Production-only fixtures."""
+
+    DEVELOPMENT = "development"
+    """Development fixtures."""
+
+    TESTING = "testing"
+    """Test fixtures."""