Initial commit: Arb Pulse monolith with CI and optional Fly deploy.

Real-time BTC cross-exchange arbitrage detection (Kraken, Bybit, OKX, Binance)
with React dashboard, GitHub Actions CI, and documented Fly.io deploy workflow.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/infrastructure/exchanges/kraken.ts

@@ -0,0 +1,56 @@
+import type { ExchangeId } from "../../domain/entities/index.js";
+import { ExchangeConnector } from "./base.js";
+
+interface KrakenLevel {
+  price: number;
+  qty: number;
+}
+
+interface KrakenBookData {
+  symbol: string;
+  bids: KrakenLevel[];
+  asks: KrakenLevel[];
+  timestamp?: string;
+}
+
+interface KrakenMessage {
+  channel?: string;
+  type?: "snapshot" | "update";
+  data?: KrakenBookData[];
+}
+
+/**
+ * Kraken WebSocket v2 — `book` channel.
+ * Docs: https://docs.kraken.com/websockets-v2/
+ * Snapshot replaces the book; updates patch individual price levels (qty 0 = remove).
+ */
+export class KrakenConnector extends ExchangeConnector {
+  readonly id: ExchangeId = "kraken";
+  protected readonly url = "wss://ws.kraken.com/v2";
+  private readonly symbol = "BTC/USDT";
+
+  protected subscribeMessage(): unknown {
+    return {
+      method: "subscribe",
+      params: { channel: "book", symbol: [this.symbol], depth: 10 },
+    };
+  }
+
+  protected handleMessage(msg: unknown): void {
+    const m = msg as KrakenMessage;
+    if (m.channel !== "book" || !Array.isArray(m.data)) return;
+
+    const data = m.data[0];
+    if (!data) return;
+
+    if (m.type === "snapshot") {
+      this.book.reset();
+    }
+
+    for (const lvl of data.bids ?? []) this.book.bids.apply(lvl.price, lvl.qty);
+    for (const lvl of data.asks ?? []) this.book.asks.apply(lvl.price, lvl.qty);
+
+    const exchangeTs = data.timestamp ? Date.parse(data.timestamp) : null;
+    this.emit(Number.isFinite(exchangeTs) ? exchangeTs : null);
+  }
+}