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/ruff.toml

@@ -0,0 +1,9 @@
+line-length = 100
+target-version = "py311"
+
+[lint]
+select = ["E", "F", "I", "UP", "B", "C4", "SIM"]
+ignore = ["B008"]
+
+[format]
+quote-style = "double"