/claim #2332

Implements Docker-like start_period semantics for Coolify’s healthcheck retry loop (per #2200 / #2332):

• begins healthchecks immediately
• ignores failures during start period until either (a) a success occurs or (b) the start period elapses
• counts failures towards retries after start period (or after first success)

Note: #2332/#2200 also mentions notifications on health status change; I can add that in a follow-up PR if required for the bounty.

Demo video: will add a short clip showing a service failing healthchecks during start period then recovering.