Refactor web health checker & domain expectations (filter-based)

- Move all domain→expected-status mapping to filter `web_health_expectations`.
- Require explicit app selection via non-empty `group_names`; only those apps are included.
- Add `www_enabled` flag (wired via `WWW_REDIRECT_ENABLED`) to generate/force www.* → 301.
- Support `redirect_maps` to include manual redirects (sources forced to 301), independent of app selection.
- Aliases always 301; canonicals use per-key override or `server.status_codes.default`, else [200,302,301].
- Remove legacy fallbacks (`server.status_codes.home` / `landingpage`).
- Wire filter output into systemd ExecStart script as JSON expectations.
- Normalize various templates to use `to_json` and minor spacing fixes.
- Update app configs (e.g., YOURLS default=301; Confluence default=302; Bluesky web=405; MediaWiki/Confluence canonical/aliases).
- Constructor now uses `WWW_REDIRECT_ENABLED` for domain generation.

Tests:
- Add comprehensive unit tests for filter: selection by group, keyed/default codes, aliases, www handling, redirect_maps, input sanitization.
- Add unit tests for the standalone checker script (JSON parsing, OK/mismatch counting, sanitization).

See conversation: https://chatgpt.com/share/68c2b93e-de58-800f-8c16-ea05755ba776

roles/sys-ctl-hlth-webserver/tasks/01_core.yml

@@ -20,3 +20,7 @@
     system_service_timer_enabled:         true
     system_service_tpl_on_failure:        "{{ SYS_SERVICE_ON_FAILURE_COMPOSE }}"
     system_service_tpl_timeout_start_sec: "{{ CURRENT_PLAY_DOMAINS_ALL | timeout_start_sec_for_domains }}"
+    system_service_tpl_exec_start: > 
+      {{ system_service_script_exec }}
+      --web-protocol {{ WEB_PROTOCOL }}
+      --expectations '{{ applications | web_health_expectations(www_enabled=WWW_REDIRECT_ENABLED, group_names=group_names) | to_json }}'