feat: implement T22, T18, T23 — dev stack, profile tests, server binary

- T22: docker-compose.dev.yml dev stack, Dockerfile, root Makefile
- T18: Profile test suite (Scenario A) — 8 integration tests with real handlers
- T23: Server binary wiring all components, config validation, /healthz
- Config: ValidateConfig with startup validation

14 test packages pass.

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

Makefile

@@ -0,0 +1,16 @@
+.PHONY: dev seed build test lint
+
+dev:
+	docker compose -f docker-compose.dev.yml up
+
+seed:
+	docker compose -f docker-compose.dev.yml exec lldap /scripts/seed.sh
+
+build:
+	cd src && go build ./...
+
+test:
+	cd src && go test ./...
+
+lint:
+	cd src && go vet ./...