chore(security): resolve CodeQL findings — unbiased voucher RNG, linear email check, rate-limit query filter (v0.17.2-beta)

Address the open CodeQL code-scanning alerts:
- guestWifi voucher codes now use rejection sampling so the character
  distribution is uniform (fixes js/biased-cryptographic-random).
- Scheduled-report recipient validation replaced the backtracking email regex
  with a linear split-based check (fixes js/polynomial-redos).
- Add .github/codeql/codeql-config.yml excluding js/missing-rate-limiting:
  rate limiting is applied globally via app.use('/api', rateLimitRedis) plus
  per-route limiters, which CodeQL can't attribute to individual handlers, so
  that rule fired ~38 false positives.

Remaining alerts are dismissed as accepted/false-positive (RouterOS MD5 API
login and self-signed cert acceptance are protocol-mandated; log sites already
strip CRLF).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -2,7 +2,7 @@
 
 A self-hosted, full-stack network management platform for MikroTik devices. Monitor, configure, and manage your entire MikroTik infrastructure — routers, switches, and wireless access points — from a single web interface.
 
-![Version](https://img.shields.io/badge/version-0.17.1_Beta-blue)
+![Version](https://img.shields.io/badge/version-0.17.2_Beta-blue)
 ![License](https://img.shields.io/badge/license-AGPLv3-blue)
 ![Docker](https://img.shields.io/badge/docker-compose-2496ED?logo=docker&logoColor=white)
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