Add "insecure connection" warning when interacting/sharing to HTTP domain

(SetupChecks) Add the actual hostname/URL/IP that triggered the warning/error

[Bug]: Setup check for `X-Robot-Tag` expects exact match, resulting in a warning

Add a dedicated DNS‐resolution health check and admin warning for DNS failures

[RFC / Feature Proposal] Relaxing Strict PHP Upper-Bound Enforcement into Configurable Soft Warnings for Emergency Security Mitigations (e.g., `php2shell`)