refactor(healthcheck): support multiple profiles per host with aggregate result

Replace the single healthcheck_profile with a healthcheck_profiles list so a
host can run several checks (e.g. hk2: pdns, rustdesk, hk2aux). Profiles emit
per-check JSON to latest-<check>.json; the dispatcher clears stale per-check
files, runs every profile, and merges them into latest.json.

Contract: a single complete check keeps the historical verbatim latest.json
shape; several checks produce a worst-status aggregate retaining every check's
detail. A profile that crashes before reporting is aggregated as unknown so
latest.json can never go stale while the dispatcher fails. The dispatcher exits
with the worst (max) profile exit code.

ansible/roles/healthcheck/defaults/main.yml

@@ -7,9 +7,13 @@ healthcheck_timer_on_calendar: '*-*-* 06:15:00'
 healthcheck_timer_randomized_delay_sec: 15m
 healthcheck_backup_max_age_hours: 30
 healthcheck_tls_warn_days: 21
-healthcheck_profiles:
+# Map of profile name -> installed script filename. A host selects which
+# profiles it runs via the `healthcheck_profiles` list (inventory).
+healthcheck_profile_scripts:
   mailcow: mailcow.sh
   vaultwarden: vaultwarden.sh
   pdns: pdns.sh
   wireguard: wireguard.sh
   adguardhome: adguardhome.sh
+  rustdesk: rustdesk.sh
+  hk2aux: hk2aux.sh