feat: modernise cookbook structure and ChefSpec

[damacus]

Summary

Modernises the cookbook structure, spec organisation, and CI configuration.

Changes

• frozen_string_literal: Added # frozen_string_literal: true to all Ruby files
• Resources: Added provides declarations to all custom resources
• ChefSpec: Renamed spec/unit/recipes/ → spec/unit/resources/ to reflect resource-based testing
• ChefSpec: Fixed almalinux/10 spec — platform not bundled in fauxhai gem; use almalinux/9 with node.automatic['platform_version'] = '10' override to test PCRE2 branch
• metadata.rb: Expanded platform support (almalinux, rocky, oracle, fedora)
• kitchen.yml: Added default suite, aligned platforms with kitchen.dokken.yml, switched provisioner to chef_infra
• CI: Aligned matrix with kitchen platforms and suites, added missing platforms, removed duplicates
• LIMITATIONS.md: Documents known constraints (package availability, source build deps, architecture)
• Integration: Added default test suite with test recipe and InSpec profile

Testing

• 29/29 ChefSpec examples pass, 0 failures, no fauxhai download warnings

[github-actions]

Slowest examples

Top 10 slowest examples (1.13 seconds, 45.88% of total time)

Example	Description	Time in seconds
spec/unit/resources/frontend_backend_spec.rb:35	haproxy_frontend create frontend and backend with http-request rule placed before use_backend is expected to render file "/etc/haproxy/haproxy.cfg"	0.14976
spec/unit/resources/frontend_backend_spec.rb:36	haproxy_frontend create frontend and backend with http-request rule placed before use_backend is expected not to render file "/etc/haproxy/haproxy.cfg" with content /use_backend admin0 if path_beg /admin0.*http-request add-header Test Value/m	0.14451
spec/unit/resources/cache_spec.rb:47	haproxy_cache create a cache, frontend and backend and verify config is created properly is expected to render file "/etc/haproxy/haproxy.cfg"	0.14421
spec/unit/resources/defaults_spec.rb:28	haproxy_config_defaults create a cache, frontend and backend and verify config is created properly is expected to render file "/etc/haproxy/haproxy.cfg"	0.11528
spec/unit/resources/listen_spec.rb:84	haproxy_listen extra options hash with disabled option is expected to render file "/etc/haproxy/haproxy.cfg"	0.10665
spec/unit/resources/listen_spec.rb:108	haproxy_listen extra options http-request rule should be placed before use_backend rule is expected not to render file "/etc/haproxy/haproxy.cfg" with content /use_backend admin0 if path_beg /admin0.*http-request add-header Test Value/m	0.10233
spec/unit/resources/peer_spec.rb:47	haproxy_peer create a peers section, frontend and backend and verify config is created properly is expected to render file "/etc/haproxy/haproxy.cfg"	0.10057
spec/unit/resources/fastcgi_spec.rb:65	haproxy_fastcgi create a fastcgi resource, frontend and backend and verify config is created properly is expected to render file "/etc/haproxy/haproxy.cfg"	0.09418
spec/unit/resources/mailer_spec.rb:50	haproxy_mailer create a mailer, frontend and backend and verify config is created properly is expected to render file "/etc/haproxy/haproxy.cfg"	0.09016
spec/unit/resources/listen_spec.rb:107	haproxy_listen extra options http-request rule should be placed before use_backend rule is expected to render file "/etc/haproxy/haproxy.cfg"	0.08921