Implement ALTCHA captcha service with challenge generation and solution verification

- Added AltchaService class for managing ALTCHA captcha challenges and solutions.
- Created CaptchaController to handle API requests for generating challenges.
- Introduced CaptchaGuard for validating captcha solutions on public endpoints.
- Developed unit tests for AltchaService to ensure challenge creation and solution verification functionality.
- Implemented integration tests for the Captcha API endpoint and captcha bypass behavior when disabled.
- Added documentation for the Captcha API in the corresponding markdown file.

config/packages/cache.yaml

@@ -2,3 +2,7 @@ framework:
     cache:
         app: cache.adapter.redis
         default_redis_provider: '%env(REDIS_URL)%'
+        pools:
+            altcha.pool:
+                adapter: cache.adapter.redis
+                default_lifetime: 600