Crypto trading bot: engine, brokers, backtester, dashboard, deploy

FastAPI backend with a single-strategy async engine, paper and Binance
brokers, pure-python indicators, a backtester that shares the engine's
portfolio math, and a Vue dashboard with a live WebSocket feed. Adds the
Gitea Actions CI/CD workflow that deploys to Traefik via docker_default.

backend/requirements-dev.txt

@@ -0,0 +1,5 @@
+-r requirements.txt
+pytest>=8.3
+pytest-asyncio>=0.25
+anyio>=4.7
+ruff>=0.8