refactor: comprehensive code review fixes and security hardening

Security:
- Add CSP headers for HTML reports (style-src 'unsafe-inline')
- Restrict origin validation to specific .kappa-d8e.workers.dev domain
- Add base64 size limit (100KB) for report data parameter
- Implement rejection sampling for unbiased password generation
- Add SQL LIKE pattern escaping for tech specs query
- Add security warning for plaintext password storage (TODO: encrypt)

Performance:
- Add Telegram API timeout (10s) with AbortController
- Fix rate limiter sorting by resetTime for proper cleanup
- Use centralized TIMEOUTS config for VPS provider APIs

Features:
- Add admin SSH key support for server recovery access
  - ADMIN_SSH_PUBLIC_KEY for Linode (public key string)
  - ADMIN_SSH_KEY_ID_VULTR for Vultr (pre-registered key ID)
- Add origin validation middleware
- Add idempotency key migration

Code Quality:
- Return 404 status when no servers found
- Consolidate error logging to single JSON.stringify call
- Import TECH_CATEGORY_WEIGHTS from config.ts
- Add escapeLikePattern utility function

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/handlers/health.ts

@@ -2,19 +2,17 @@
  * Health check endpoint handler
  */
 
-import { jsonResponse } from '../utils';
+import type { Context } from 'hono';
+import type { Env } from '../types';
 
 /**
  * Health check endpoint
  */
-export function handleHealth(corsHeaders: Record<string, string>): Response {
-  return jsonResponse(
-    {
-      status: 'ok',
-      timestamp: new Date().toISOString(),
-      service: 'server-recommend',
-    },
-    200,
-    corsHeaders
-  );
+export function handleHealth(c: Context<{ Bindings: Env }>) {
+  return c.json({
+    status: 'ok',
+    timestamp: new Date().toISOString(),
+    service: 'server-recommend',
+    request_id: c.get('requestId'),
+  });
 }