app-email: calcom+nextcloud wired & send-tested; calcom healthcheck GET fix + docs

calcom + nextcloud both send live via the :2526 plaintext listener (calcom signup =
Nodemailer; nextcloud password-reset = Symfony Mailer), both From <app>@felhom.eu.
calcom healthcheck: wget GET not --spider (HEAD 405s). CHANGELOG + REPORT.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

templates/calcom/docker-compose.yml

@@ -41,7 +41,8 @@ services:
         limits:
           memory: 768M
     healthcheck:
-      test: ["CMD", "wget", "--spider", "-q", "http://localhost:3000/api/auth/providers"]
+      # GET (-O /dev/null), not --spider (HEAD): the Next.js API route rejects HEAD, so --spider flaps unhealthy.
+      test: ["CMD", "wget", "-q", "-O", "/dev/null", "http://localhost:3000/api/auth/providers"]
       interval: 30s
       timeout: 5s
       retries: 3