fix: Add explicit constraint name in mtime/size migration

SQLite batch operations require explicit constraint names.
Changed from `None` to `batch_op.f("fk_entity_project_id")` to fix
migration error: "Constraint must have a name"

Fixes cloud deployment migration failure.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: phernandez

src/basic_memory/alembic/versions/9d9c1cb7d8f5_add_mtime_and_size_columns_to_entity_.py

@@ -25,15 +25,19 @@ def upgrade() -> None:
         batch_op.add_column(sa.Column("mtime", sa.Float(), nullable=True))
         batch_op.add_column(sa.Column("size", sa.Integer(), nullable=True))
         batch_op.drop_constraint(batch_op.f("fk_entity_project_id"), type_="foreignkey")
-        batch_op.create_foreign_key(None, "project", ["project_id"], ["id"])
+        batch_op.create_foreign_key(
+            batch_op.f("fk_entity_project_id"), "project", ["project_id"], ["id"]
+        )
 
     # ### end Alembic commands ###
 
 
 def downgrade() -> None:
     # ### commands auto generated by Alembic - please adjust! ###
     with op.batch_alter_table("entity", schema=None) as batch_op:
-        batch_op.drop_constraint(None, type_="foreignkey")  # pyright: ignore [reportArgumentType]
+        batch_op.drop_constraint(
+            batch_op.f("fk_entity_project_id"), type_="foreignkey"
+        )
         batch_op.create_foreign_key(
             batch_op.f("fk_entity_project_id"),
             "project",