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/app/broker/__init__.py

@@ -0,0 +1,20 @@
+from __future__ import annotations
+
+from app.broker.base import Broker, Fill
+from app.broker.binance import TESTNET_URL, BinanceBroker
+from app.broker.paper import PaperBroker
+from app.config import Settings
+from app.market.binance import BASE_URL
+
+
+def build_broker(settings: Settings) -> Broker:
+    if settings.mode == "live":
+        return BinanceBroker(
+            api_key=settings.exchange_api_key,
+            api_secret=settings.exchange_api_secret,
+            base_url=TESTNET_URL if settings.exchange_sandbox else BASE_URL,
+        )
+    return PaperBroker(fee_bps=settings.fee_bps, slippage_bps=settings.slippage_bps)
+
+
+__all__ = ["Broker", "Fill", "PaperBroker", "build_broker"]