fix(app): add rate limiting to all API endpoints

Add sliding-window rate limiter in server/dev-auth.ts (60 req/min reads,
10 req/min writes per IP). Apply checkRateLimit() in all Vite plugins
and claude-proxy.ts after auth validation.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/app/server/dev-auth.ts

@@ -1,5 +1,5 @@
 /**
- * Shared dev server authentication middleware.
+ * Shared dev server authentication and rate limiting middleware.
  * Validates Bearer token on all /api/* requests.
  * Token is auto-generated in scripts/dev.sh and injected via VITE_DEV_API_TOKEN.
  */
@@ -7,7 +7,6 @@ import type { IncomingMessage, ServerResponse } from 'http'
 
 const DEV_TOKEN = process.env.VITE_DEV_API_TOKEN ?? ''
 
-/** Validate Authorization header. Returns true if authorized, false if rejected (response already sent). */
 /** Validate Authorization header. Returns true if authorized, false if rejected (response already sent). */
 export function validateDevAuth(req: IncomingMessage, res: ServerResponse): boolean {
   if (!DEV_TOKEN) return true // No token configured, skip auth
@@ -34,3 +33,53 @@ export function handleCorsOptions(res: ServerResponse): void {
   })
   res.end()
 }
+
+// ─── Rate Limiting ──────────────────────────────────────────
+
+const WINDOW_MS = 60_000 // 1 minute window
+const READ_LIMIT = 60 // 60 requests per minute for reads
+const WRITE_LIMIT = 10 // 10 requests per minute for writes
+
+interface RateBucket {
+  count: number
+  resetAt: number
+}
+
+const rateBuckets = new Map<string, RateBucket>()
+
+// Clean up stale buckets every 5 minutes
+setInterval(() => {
+  const now = Date.now()
+  for (const [key, bucket] of rateBuckets) {
+    if (now > bucket.resetAt) rateBuckets.delete(key)
+  }
+}, 5 * 60_000)
+
+function getClientIp(req: IncomingMessage): string {
+  return req.socket.remoteAddress ?? 'unknown'
+}
+
+/**
+ * Check rate limit for a request. Returns true if allowed, false if rejected (response already sent).
+ * @param isWrite - Set to true for write operations (POST/PUT/DELETE) which have a lower limit.
+ */
+export function checkRateLimit(req: IncomingMessage, res: ServerResponse, isWrite = false): boolean {
+  const ip = getClientIp(req)
+  const limit = isWrite ? WRITE_LIMIT : READ_LIMIT
+  const key = `${ip}:${isWrite ? 'w' : 'r'}`
+  const now = Date.now()
+
+  let bucket = rateBuckets.get(key)
+  if (!bucket || now > bucket.resetAt) {
+    bucket = { count: 0, resetAt: now + WINDOW_MS }
+    rateBuckets.set(key, bucket)
+  }
+
+  bucket.count++
+  if (bucket.count > limit) {
+    res.writeHead(429, { 'Content-Type': 'application/json', 'Retry-After': '60' })
+    res.end(JSON.stringify({ error: 'Too many requests' }))
+    return false
+  }
+  return true
+}