chore: add one-click setup/start/stop scripts, migration CLI, and seed tool

- Add idempotent seed tool with duplicate detection for agents/issues/comments
- Add migration CLI supporting up/down with schema_migrations tracking
- Add Makefile targets: make setup (first-time), make start, make stop
- Update .gitignore for test artifacts and compiled binaries

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Makefile

@@ -1,4 +1,45 @@
-.PHONY: dev daemon build test migrate-up migrate-down sqlc seed clean
+.PHONY: dev daemon build test migrate-up migrate-down sqlc seed clean setup start stop
+
+# ---------- One-click commands ----------
+
+# First-time setup: install deps, start DB, run migrations, seed data
+setup:
+	@echo "==> Installing dependencies..."
+	pnpm install
+	@echo "==> Starting PostgreSQL..."
+	docker compose up -d
+	@echo "==> Waiting for PostgreSQL to be ready..."
+	@until docker compose exec -T postgres pg_isready -U multica > /dev/null 2>&1; do \
+		sleep 1; \
+	done
+	@echo "==> Running migrations..."
+	cd server && go run ./cmd/migrate up
+	@echo "==> Seeding data..."
+	cd server && go run ./cmd/seed
+	@echo ""
+	@echo "✓ Setup complete! Run 'make start' to launch the app."
+
+# Start all services (backend + frontend)
+start:
+	@docker compose up -d
+	@until docker compose exec -T postgres pg_isready -U multica > /dev/null 2>&1; do \
+		sleep 1; \
+	done
+	@echo "Starting backend and frontend..."
+	@trap 'kill 0' EXIT; \
+		(cd server && go run ./cmd/server) & \
+		pnpm dev:web & \
+		wait
+
+# Stop all services
+stop:
+	@echo "Stopping services..."
+	@-lsof -ti:8080 | xargs kill -9 2>/dev/null
+	@-lsof -ti:3000 | xargs kill -9 2>/dev/null
+	docker compose down
+	@echo "✓ All services stopped."
+
+# ---------- Individual commands ----------
 
 # Go server
 dev: