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.

.env.example

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+# --- Core ---
+APP_NAME=Crypto Trader
+ENV=dev
+# API host/port
+HOST=0.0.0.0
+PORT=8000
+
+# --- Persistence ---
+# SQLite by default. Point at Postgres with e.g.
+# postgresql+psycopg://user:pass@localhost:5432/trader
+DATABASE_URL=sqlite:///./data/trader.db
+
+# --- Trading defaults ---
+# paper = simulated fills against live market data (safe default)
+# live  = real orders via the exchange
+MODE=paper
+EXCHANGE=binance
+SYMBOL=BTC/USDT
+TIMEFRAME=1m
+# How often the engine polls for new candles, in seconds
+POLL_INTERVAL=5
+# Candles fetched per tick and kept for indicators
+CANDLE_LIMIT=200
+
+# Paper broker
+STARTING_BALANCE=10000
+FEE_BPS=10
+SLIPPAGE_BPS=5
+
+# --- Exchange credentials (only needed for MODE=live) ---
+EXCHANGE_API_KEY=
+EXCHANGE_API_SECRET=
+# Set true for testnet/sandbox where supported
+EXCHANGE_SANDBOX=false
+
+# --- Web ---
+# Comma separated list, or * in dev
+CORS_ORIGINS=*