refactor: tighten backend, flows, frontend, tests; push flows to Langflow

backend/app/models/base.py

@@ -0,0 +1,18 @@
+"""Shared SQLModel base: UTC timestamps, no copy-paste across models."""
+
+from datetime import UTC, datetime
+
+from sqlalchemy import Column, DateTime
+from sqlmodel import Field
+
+
+def utcnow() -> datetime:
+    return datetime.now(UTC)
+
+
+def ts_column() -> Column:
+    return Column(DateTime(timezone=True))
+
+
+def ts_field(*, default_factory=utcnow) -> datetime:  # type: ignore[no-untyped-def]
+    return Field(default_factory=default_factory, sa_column=ts_column())