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/paper.py

@@ -0,0 +1,38 @@
+from __future__ import annotations
+
+from app.broker.base import Broker, Fill
+from app.models import OrderSide, utcnow
+
+
+class PaperBroker(Broker):
+    """Simulated fills against a reference price, with fees and slippage.
+
+    Buys fill slightly above and sells slightly below the reference price to
+    approximate adverse slippage.
+    """
+
+    def __init__(self, fee_bps: float = 10.0, slippage_bps: float = 5.0) -> None:
+        self.fee_bps = fee_bps
+        self.slippage_bps = slippage_bps
+
+    def _fee(self, notional: float) -> float:
+        return abs(notional) * self.fee_bps / 10_000
+
+    def fill(self, symbol: str, side: OrderSide, qty: float, ref_price: float) -> Fill:
+        """Synchronous fill used by the backtester (same model as buy/sell)."""
+        direction = 1 if side == OrderSide.BUY else -1
+        price = ref_price * (1 + direction * self.slippage_bps / 10_000)
+        return Fill(
+            symbol=symbol,
+            side=side,
+            qty=qty,
+            price=price,
+            fee=self._fee(qty * price),
+            ts=utcnow(),
+        )
+
+    async def buy(self, symbol: str, qty: float, ref_price: float) -> Fill:
+        return self.fill(symbol, OrderSide.BUY, qty, ref_price)
+
+    async def sell(self, symbol: str, qty: float, ref_price: float) -> Fill:
+        return self.fill(symbol, OrderSide.SELL, qty, ref_price)