test: add test tooling and documentation

- Add Makefile with convenient test targets (test, test-integration, test-env-up, test-env-down)
- Add .env.test with test-specific configuration
- Update .env.example with test configuration options and warnings
- Update README.md with comprehensive testing documentation
- Document all environment variables with safety warnings

This makes it easy to run tests without rate limiting issues while
keeping production security intact.

Makefile

@@ -0,0 +1,59 @@
+.PHONY: help test test-integration test-all build build-force clean rebuild logs test-env-up test-env-down
+
+# Default target
+help:
+	@echo "Available targets:"
+	@echo "  make test              - Run unit tests"
+	@echo "  make test-integration  - Run integration tests with test mode enabled"
+	@echo "  make test-all          - Run all tests"
+	@echo "  make build             - Build and start containers"
+	@echo "  make build-force       - Force rebuild and start containers"
+	@echo "  make clean             - Stop and remove containers"
+	@echo "  make rebuild           - Clean, rebuild, and start containers"
+	@echo "  make logs              - Show container logs"
+	@echo "  make test-env-up       - Start containers with test mode enabled"
+	@echo "  make test-env-down     - Stop test environment"
+
+# Run unit tests
+test:
+	go test ./... -v -short
+
+# Run integration tests with test mode enabled (avoids rate limiting)
+test-integration:
+	@echo "Running integration tests with TEST_MODE enabled..."
+	TEST_MODE=true RATE_LIMIT_ENABLED=false go test ./cmd/server/tests -run TestIntegrationAPI -v -timeout 5m
+
+# Run all tests
+test-all: test test-integration
+
+# Build and start containers
+build:
+	podman compose up --build -d
+
+# Force rebuild without cache
+build-force:
+	podman compose build --no-cache
+	podman compose up -d
+
+# Stop and remove containers
+clean:
+	podman compose down -v
+
+# Clean rebuild (remove volumes, rebuild, start)
+rebuild: clean build
+
+# Show container logs
+logs:
+	podman compose logs -f
+
+# Start containers with test mode enabled for integration testing
+test-env-up:
+	@echo "Starting containers with test mode enabled..."
+	TEST_MODE=true RATE_LIMIT_ENABLED=false REQUESTS_PER_MINUTE=1000 podman compose up --build -d
+	@echo "Waiting for services to be ready..."
+	sleep 10
+	@echo "Test environment is ready!"
+
+# Stop test environment
+test-env-down:
+	podman compose down -v