Add swing trading strategy with RSI signals and Binance integration

- Introduced a new swing trading strategy utilizing the RSI indicator on the ETHBTC pair from Binance.
- Implemented the `SwingEngine` to manage trading logic, including entry and exit conditions based on RSI thresholds.
- Added configuration options for swing direction, trade amount, and RSI parameters in `config.ts`.
- Created new documentation for the swing strategy, detailing its behavior and configuration.
- Enhanced CLI to support the new swing strategy option.
- Added tests for swing logic to ensure correct behavior under various market conditions.

docs/swingtrading/runbook.md

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+# Swing strategy (RSI on Binance ETHBTC)
+
+This repo’s `swing` strategy **trades the exchange symbol you run the bot with** (e.g. `TRADE_SYMBOL`), but **uses Binance spot `ETHBTC` 4h RSI(14)** as the global signal source (per `docs/swingtrading/strategy.md`).
+
+## Key behavior
+
+- **Signal source**: Binance spot `ETHBTC`, `4h` klines, RSI period `14`.
+- **Trade target**: your selected exchange’s `TRADE_SYMBOL` / `*_SYMBOL` (same as other strategies).
+- **Default mode**: short-only (configurable to long / short / both).
+- **Stop-loss**:
+  - Tries to place a stop-loss order when supported by the venue.
+  - Always runs a real-time “kill-switch”: if price crosses the stop threshold, it market-closes.
+- **Spot accounts**: if the connected account is `marketType=spot` and you configure `SWING_DIRECTION=short` (or `both`), the strategy will refuse to trade.
+
+## Environment variables
+
+- **Core**
+  - `SWING_DIRECTION`: `short` (default) | `long` | `both`
+  - `SWING_TRADE_AMOUNT`: position size (falls back to `TRADE_AMOUNT`)
+  - `SWING_POLL_INTERVAL_MS`: loop interval (default `500`)
+- **RSI / signal**
+  - `SWING_RSI_PERIOD`: default `14`
+  - `SWING_RSI_HIGH`: default `70`
+  - `SWING_RSI_LOW`: default `30`
+  - `SWING_SIGNAL_SYMBOL`: default `ETHBTC`
+  - `SWING_SIGNAL_INTERVAL`: default `4h`
+- **Risk / precision**
+  - `SWING_STOP_LOSS_PCT`: default `0.05` (5%)
+  - `SWING_MAX_CLOSE_SLIPPAGE_PCT`: default `0.05`
+  - `SWING_PRICE_TICK`, `SWING_QTY_STEP`: optional overrides (otherwise synced from exchange when supported)
+
+## Run
+
+```bash
+bun run index.ts --strategy swing
+```
+
+Silent mode:
+
+```bash
+bun run index.ts --strategy swing --silent
+```
+