fix: inline test-api.html as TypeScript string export for Vercel

Bun import of .html files returns HTMLBundle (not a string) in Vercel's
serverless environment, and Bun.file() has no filesystem access there.
Copy the HTML content into api/test-api-content.ts as an escaped string
export, then import it in api/relay.ts — Bun bundler inlines it.

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

api/relay.ts

@@ -29,10 +29,7 @@ import { createRateLimiter } from "../src/middleware/rate-limiter";
 import { logRelayEvent } from "../src/middleware/logger";
 import { handleChatCompletion, listModels } from "../src/lib/ai-proxy";
 import { handleAnthropicMessages } from "../src/lib/anthropic-proxy";
-
-// Read test-api.html at module scope so Bun's bundler inlines the content
-// at build time (Vercel serverless has no filesystem at runtime).
-const testApiHtmlRaw = await Bun.file("public/test-api.html").text();
+import testApiHtmlRaw from "./test-api-content";
 
 // ─── Configuration ──────────────────────────────────────────────────────────────
 

api/test-api-content.ts

@@ -0,0 +1 @@
+export default "<!DOCTYPE html>\n<html lang=\"en\">\n<head>\n  <meta charset=\"UTF-8\">\n  <meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0\">\n  <title>Edge Proxy — API Test</title>\n  <style>\n    *, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }\n    body { font-family: system-ui, -apple-system, sans-serif; background: #0d1117; color: #e1e4e8; padding: 1.5rem; }\n    main { max-width: 960px; margin: 0 auto; }\n    h1 { font-size: 1.5rem; colorLine truncated