Fix SonarQube issues, store sessions in Redis, use direct analytics URLs

- ApiSandboxController: reduce scan() returns from 4 to 3 via ternary
- ApiDocController: add MIME_JSON constant, extract buildInsomniaRequest()
  and buildInsomniaBody() to reduce cognitive complexity
- Store sessions in Redis to fix SSO disconnect with 2 PHP replicas
  (round-robin load balancing caused session loss on filesystem storage)
- Configure session cookie: 24h lifetime, secure auto, samesite lax
- Replace Caddy analytics proxies (/stats/*, /assets/perf.js, /sperf)
  with direct URLs to tools-security.esy-web.dev and cloudflareinsights.com
- Update JS tests for new direct analytics URLs

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

config/reference.php

@@ -1271,9 +1271,9 @@ use Symfony\Component\Config\Loader\ParamConfigurator as Param;
  *             lifetime?: int|Param, // Default: 31536000
  *             path?: scalar|Param|null, // Default: "/"
  *             domain?: scalar|Param|null, // Default: null
- *             secure?: true|false|"auto"|Param, // Default: false
+ *             secure?: true|false|"auto"|Param, // Default: null
  *             httponly?: bool|Param, // Default: true
- *             samesite?: null|"lax"|"strict"|"none"|Param, // Default: null
+ *             samesite?: null|"lax"|"strict"|"none"|Param, // Default: "lax"
  *             always_remember_me?: bool|Param, // Default: false
  *             remember_me_parameter?: scalar|Param|null, // Default: "_remember_me"
  *         },