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/base.py

@@ -0,0 +1,36 @@
+from __future__ import annotations
+
+from abc import ABC, abstractmethod
+from dataclasses import dataclass
+from datetime import datetime
+
+from app.models import OrderSide
+
+
+@dataclass(slots=True)
+class Fill:
+    symbol: str
+    side: OrderSide
+    qty: float
+    price: float
+    fee: float
+    ts: datetime
+
+    @property
+    def notional(self) -> float:
+        return self.qty * self.price
+
+
+class Broker(ABC):
+    """Executes market orders. Paper and live brokers share this interface."""
+
+    @abstractmethod
+    async def buy(self, symbol: str, qty: float, ref_price: float) -> Fill:
+        raise NotImplementedError
+
+    @abstractmethod
+    async def sell(self, symbol: str, qty: float, ref_price: float) -> Fill:
+        raise NotImplementedError
+
+    async def close(self) -> None:
+        return None