add dev user script

Makefile

@@ -1,3 +1,19 @@
+# Local development user. Override DATABASE_URL/DEV_USER_* when needed.
+DATABASE_URL ?= postgresql://postgres:postgres@localhost:5432/evening_detective_server?sslmode=disable
+DEV_USER_USERNAME ?= dev
+DEV_USER_EMAIL ?= dev@example.com
+DEV_USER_PASSWORD ?= dev123456
+
+.PHONY: dev-user
+
+dev-user:
+	psql "$(DATABASE_URL)" \
+		-v ON_ERROR_STOP=1 \
+		-v dev_username="$(DEV_USER_USERNAME)" \
+		-v dev_email="$(DEV_USER_EMAIL)" \
+		-v dev_password="$(DEV_USER_PASSWORD)" \
+		-f scripts/dev-user.sql
+
 # Protobuf generation (tool versions are documented in README.md).
 # Install the pinned plugins before running: make install-generate-tools.
 generate: