Moved models to shared base

app/db/base_class.py

@@ -0,0 +1,13 @@
+from sqlalchemy import MetaData
+from sqlalchemy.orm import declarative_base
+
+# Optional: naming convention keeps Alembic diffs stable
+convention = {
+    "ix": "ix_%(column_0_label)s",
+    "uq": "uq_%(table_name)s_%(column_0_name)s",
+    "ck": "ck_%(table_name)s_%(constraint_name)s",
+    "fk": "fk_%(table_name)s_%(column_0_name)s_%(referred_table_name)s",
+    "pk": "pk_%(table_name)s",
+}
+metadata = MetaData(naming_convention=convention)
+Base = declarative_base(metadata=metadata)