feat: implement persistent audit logging for import/export operations with Prometheus metrics

models/import_export_log.py

@@ -0,0 +1,32 @@
+from __future__ import annotations
+
+from datetime import datetime
+
+from sqlalchemy import Column, DateTime, ForeignKey, Integer, String, Text
+from sqlalchemy.sql import func
+
+from config.database import Base
+
+
+class ImportExportLog(Base):
+    """Audit log for import and export operations."""
+
+    __tablename__ = "import_export_logs"
+
+    id = Column(Integer, primary_key=True, index=True)
+    action = Column(String(32), nullable=False)  # preview, commit, export
+    dataset = Column(String(32), nullable=False)  # projects, scenarios, etc.
+    status = Column(String(16), nullable=False)  # success, failure
+    filename = Column(String(255), nullable=True)
+    row_count = Column(Integer, nullable=True)
+    detail = Column(Text, nullable=True)
+    user_id = Column(Integer, ForeignKey("users.id"), nullable=True)
+    created_at = Column(
+        DateTime(timezone=True), nullable=False, server_default=func.now()
+    )
+
+    def __repr__(self) -> str:  # pragma: no cover
+        return (
+            f"ImportExportLog(id={self.id}, action={self.action}, "
+            f"dataset={self.dataset}, status={self.status})"
+        )