feat: migrate from Next.js to pure Bun relay proxy

- Replace Next.js app router with standalone Bun.serve() entry point
- Add middleware stack: rate limiter, body limiter, structured logger, SSRF protection
- Add WebSocket bidirectional relay via x-relay-target header
- Implement error classification (DNS→502, timeouts→504, SSRF→403, rate→429)
- Remove all Next.js dependencies and config files
- Update deploy workflow, tsconfig, wrangler config for Bun deployment

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/index.test.ts

@@ -0,0 +1,137 @@
+/**
+ * Integration tests for the relay proxy server handlers.
+ *
+ * Tests the exported route handler functions directly,
+ * bypassing the HTTP server layer.
+ */
+
+import { test, expect, describe, beforeAll, afterAll } from "bun:test";
+
+// Import handler functions directly from index.ts
+// Note: this will also start the Bun.serve() instance, which we allow.
+import {
+	handleHealth,
+	handleDocs,
+	handleIndex,
+	getClientIP,
+} from "./index";
+
+describe("handleHealth", () => {
+	test("should return 200 with JSON body", async () => {
+		const response = handleHealth();
+		expect(response.status).toBe(200);
+		expect(response.headers.get("Content-Type")).toBe("application/json");
+	});
+
+	test("should include status, uptime, and version fields", async () => {
+		const response = handleHealth();
+		const body = await response.json();
+		expect(body.status).toBe("ok");
+		expect(typeof body.uptime).toBe("number");
+		expect(body.version).toBe("1.0.0");
+	});
+
+	test("should include CORS header", () => {
+		const response = handleHealth();
+		expect(response.headers.get("Access-Control-Allow-Origin")).toBe("*");
+	});
+});
+
+describe("handleDocs", () => {
+	test("should return 200 with HTML content", () => {
+		const response = handleDocs();
+		expect(response.status).toBe(200);
+		expect(response.headers.get("Content-Type")).toContain("text/html");
+	});
+
+	test("should include Edge Proxy Relay in the HTML", async () => {
+		const response = handleDocs();
+		const text = await response.text();
+		expect(text).toContain("Edge Proxy Relay");
+		expect(text).toContain("x-relay-target");
+		expect(text).toContain("WebSocket");
+	});
+
+	test("should include CORS header", () => {
+		const response = handleDocs();
+		expect(response.headers.get("Access-Control-Allow-Origin")).toBe("*");
+	});
+});
+
+describe("handleIndex", () => {
+	test("should return 200 with HTML content", () => {
+		const response = handleIndex();
+		expect(response.status).toBe(200);
+		expect(response.headers.get("Content-Type")).toContain("text/html");
+	});
+
+	test("should include Edge Proxy Relay title", async () => {
+		const response = handleIndex();
+		const text = await response.text();
+		expect(text).toContain("Edge Proxy Relay");
+		expect(text).toContain("Server is running");
+	});
+});
+
+describe("getClientIP", () => {
+	const mockIpGetter = (address: string) => ({
+		requestIP(_req: Request) {
+			return { address, family: "IPv4" as const, port: 12345 };
+		},
+	});
+
+	const nullIpGetter = {
+		requestIP(_req: Request) {
+			return null;
+		},
+	};
+
+	test("should return x-forwarded-for when present", () => {
+		const req = new Request("http://localhost/test", {
+			headers: { "x-forwarded-for": "198.51.100.1" },
+		});
+		const ip = getClientIP(req, nullIpGetter);
+		expect(ip).toBe("198.51.100.1");
+	});
+
+	test("should use first IP from x-forwarded-for list", () => {
+		const req = new Request("http://localhost/test", {
+			headers: {
+				"x-forwarded-for": "198.51.100.1, 203.0.113.5, 192.0.2.10",
+			},
+		});
+		const ip = getClientIP(req, nullIpGetter);
+		expect(ip).toBe("198.51.100.1");
+	});
+
+	test("should fall back to cf-connecting-ip", () => {
+		const req = new Request("http://localhost/test", {
+			headers: { "cf-connecting-ip": "203.0.113.50" },
+		});
+		const ip = getClientIP(req, nullIpGetter);
+		expect(ip).toBe("203.0.113.50");
+	});
+
+	test("should prefer x-forwarded-for over cf-connecting-ip", () => {
+		const req = new Request("http://localhost/test", {
+			headers: {
+				"x-forwarded-for": "198.51.100.1",
+				"cf-connecting-ip": "203.0.113.50",
+			},
+		});
+		const ip = getClientIP(req, nullIpGetter);
+		expect(ip).toBe("198.51.100.1");
+	});
+
+	test("should fall back to server.requestIP when no headers present", () => {
+		const req = new Request("http://localhost/test");
+		const ip = getClientIP(req, mockIpGetter("10.0.0.42"));
+		expect(ip).toBe("10.0.0.42");
+	});
+
+	test("should return unknown when nothing is available", () => {
+		const req = new Request("http://localhost/test");
+		const ip = getClientIP(req, nullIpGetter);
+		expect(ip).toBe("unknown");
+	});
+});