Document trusted-server.example.toml and restore supported config sections

Rework the app-config template so the required minimum (publisher, ec
passphrase, admin handler) is active and documented, while every optional
section and integration is commented out with a one-line description.

Restore sections that still map to live config structs but had been dropped
from the template: tester_cookie, rewrite, consent, image_optimizer, tinybird,
osano, publisher.max_buffered_body_bytes, sourcepoint.auth_cookie_name,
datadome protection fields, and prebid override rules. All example hosts stay
on example.com.

Keep the gpt, didomi, datadome, and google_tag_manager sections active with
enabled = false so the ts audit CLI can still flip them in place.

Author: aram356