chore: add Makefile + .env.example for rmi-backend

Makefile: standard targets (install/dev/build/lint/format/check/
typecheck/test/test-all/security/ci/clean) matching fleet convention.

.env.example: documents all env vars used by the backend:
- Runtime, Database, Auth, CORS, Rate limiting
- AI providers (Ollama, OpenRouter, DeepSeek, HuggingFace)
- Langfuse observability
- External APIs (CoinGecko, Etherscan, Birdeye, GoPlus, Basescan)
- Supabase, Telegram bot, Scan limits, Apify, RAG

Makefile

@@ -0,0 +1,49 @@
+.PHONY: help install dev build lint format check test typecheck security ci clean
+
+help: ## Show this help
+	@grep -E '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "  \033[36m%-20s\033[0m %s\n", $$1, $$2}'
+
+install: ## Install dependencies
+	pip install -e ".[dev]"
+	pip install -r requirements.txt
+
+dev: ## Start dev server
+	uvicorn app.main:app --reload --host 0.0.0.0 --port 8000
+
+build: ## Build Docker image
+	docker build -t rmi-backend .
+
+lint: ## Lint with ruff
+	ruff check app/ tests/
+
+format: ## Format with ruff (writes)
+	ruff format app/ tests/
+	ruff check --fix app/ tests/
+
+check: ## Full check: lint + format + typecheck + test
+	ruff check app/ tests/
+	ruff format --check app/ tests/
+	mypy app/ --ignore-missing-imports
+	pytest tests/ -x -q -m "not integration"
+
+typecheck: ## MyPy type check
+	mypy app/ --ignore-missing-imports
+
+test: ## Run tests (non-integration)
+	pytest tests/ -x -q -m "not integration"
+
+test-all: ## Run ALL tests including integration
+	pytest tests/ -q
+
+security: ## Security audit
+	bandit -r app/ -q
+	ruff check --select S app/ tests/
+
+ci: ## Full CI pipeline
+	ruff check app/ tests/
+	ruff format --check app/ tests/
+	mypy app/ --ignore-missing-imports
+	pytest tests/ -x -q -m "not integration"
+
+clean: ## Remove build artifacts
+	rm -rf dist build *.egg-info .pytest_cache .mypy_cache .ruff_cache