feat: WireGuard metrics collector + integration test stack

Metrics collector (wiregui/collector.py):
- Standalone process spawned by web app when WG_METRICS_ENABLED=true
- Polls wg show dump every WG_METRICS_POLL_INTERVAL seconds (default 5)
- Updates device stats in PostgreSQL
- Pushes Prometheus-format metrics to VictoriaMetrics (if configured)
- Graceful shutdown on SIGTERM

Integration test stack (compose.yml):
- Unified compose file for dev, test, and integration modes
- VictoriaMetrics single-node TSDB for metrics storage
- 3 mock WireGuard client containers generating ping traffic
- Automated setup script seeds server keypair, admin user, client devices
- make test-stack-up: one command to start everything
- make test-stack-verify: validates metrics flowing end-to-end

Infrastructure:
- Makefile with targets for dev, test, integration, and production
- Integration tests verify VictoriaMetrics has data for all 3 clients
- Fix Dockerfile to include img/ directory
- Separate TESTS.md for test tracking, clean TODO.md for features only

Makefile

@@ -0,0 +1,123 @@
+.PHONY: help install migrate dev dev-up dev-down dev-logs \
+       test test-unit test-e2e test-e2e-headed \
+       test-stack-up test-stack-seed test-stack-down test-stack-logs test-stack-verify \
+       prod-build \
+       clean
+
+# Default target
+help:
+	@echo "WireGUI — available targets:"
+	@echo ""
+	@echo "  Development (app runs on host, infra in Docker):"
+	@echo "    make install          Install dependencies (uv sync)"
+	@echo "    make migrate          Run database migrations"
+	@echo "    make dev              Start infra + mock IdPs, run app locally"
+	@echo "    make dev-up           Start infra only (Postgres, Valkey, mock IdPs)"
+	@echo "    make dev-down         Stop all containers"
+	@echo "    make dev-logs         Tail container logs"
+	@echo ""
+	@echo "  Testing:"
+	@echo "    make test             Run unit + e2e tests"
+	@echo "    make test-unit        Run unit tests only"
+	@echo "    make test-e2e         Run e2e tests (headless)"
+	@echo "    make test-e2e-headed  Run e2e tests in headed mode (visible browser)"
+	@echo ""
+	@echo "  Integration stack (containerized WireGUI + WG clients + VictoriaMetrics):"
+	@echo "    make test-stack-up    Seed DB, build, start everything"
+	@echo "    make test-stack-down  Stop and remove containers + volumes"
+	@echo "    make test-stack-logs  Tail logs"
+	@echo "    make test-stack-verify  Verify metrics flowing to VictoriaMetrics"
+	@echo ""
+	@echo "  Production:"
+	@echo "    make prod-build       Build production Docker image"
+	@echo ""
+	@echo "  Housekeeping:"
+	@echo "    make clean            Remove generated files, caches, volumes"
+
+# ---------------------------------------------------------------------------
+# Development
+# ---------------------------------------------------------------------------
+
+install:
+	uv sync
+
+migrate:
+	uv run alembic upgrade head
+
+dev-up:
+	docker compose up -d postgres valkey mock-oidc mock-saml
+
+dev-down:
+	docker compose down
+
+dev-logs:
+	docker compose logs -f
+
+dev: dev-up migrate
+	uv run python -m wiregui.main
+
+# ---------------------------------------------------------------------------
+# Testing
+# ---------------------------------------------------------------------------
+
+test-unit:
+	uv run pytest tests/ --ignore=tests/e2e --ignore=tests/integration -v --tb=short
+
+test-e2e:
+	uv run pytest tests/e2e/ -v --tb=short
+
+test-e2e-headed:
+	uv run pytest tests/e2e/ --headed --slowmo 300 -v --tb=short
+
+test: test-unit test-e2e
+
+# ---------------------------------------------------------------------------
+# Integration test stack (real WireGuard + mock clients + VictoriaMetrics)
+# ---------------------------------------------------------------------------
+
+test-stack-up: test-stack-seed
+	docker compose up -d --build wiregui client1 client2 client3
+	@echo ""
+	@echo "Integration stack running:"
+	@echo "  WireGUI:          http://localhost:13000  (admin@test.local / admin123)"
+	@echo "  VictoriaMetrics:  http://localhost:8428"
+	@echo "  Mock clients:     3 peers generating traffic every 3s"
+
+test-stack-seed:
+	@echo "[*] Starting infrastructure..."
+	docker compose up -d postgres valkey victoriametrics
+	@echo "[*] Waiting for Postgres..."
+	@until docker compose exec -T postgres pg_isready -U wiregui > /dev/null 2>&1; do sleep 1; done
+	@echo "[*] Running migrations..."
+	uv run alembic upgrade head
+	@echo "[*] Seeding server keypair, admin user, and client devices..."
+	PYTHONPATH=. uv run python docker/mock-clients/setup.py
+
+test-stack-down:
+	docker compose down -v
+
+test-stack-verify:
+	uv run pytest tests/integration/ -v --tb=short
+
+test-stack-logs:
+	docker compose logs -f wiregui client1 client2 client3 victoriametrics
+
+# ---------------------------------------------------------------------------
+# Production
+# ---------------------------------------------------------------------------
+
+PROD_IMAGE ?= wiregui
+PROD_TAG ?= latest
+
+prod-build:
+	docker build --no-cache -t $(PROD_IMAGE):$(PROD_TAG) .
+
+# ---------------------------------------------------------------------------
+# Housekeeping
+# ---------------------------------------------------------------------------
+
+clean:
+	find . -type d -name __pycache__ -exec rm -rf {} + 2>/dev/null || true
+	rm -rf .pytest_cache .coverage htmlcov
+	rm -rf docker/mock-clients/configs/
+	rm -rf .nicegui/