feat(deploy): V4 migration — add created_by to deployments

cameleer-server-app/src/main/resources/db/migration/V4__add_deployment_created_by.sql

@@ -0,0 +1,8 @@
+-- V4: add created_by column to deployments for audit trail
+-- Captures which user initiated a deployment. Nullable for backwards compatibility;
+-- pre-V4 historical deployments will have NULL.
+
+ALTER TABLE deployments
+    ADD COLUMN created_by TEXT REFERENCES users(user_id);
+
+CREATE INDEX idx_deployments_created_by ON deployments (created_by);