Point email links at conchecker.scoutitsystems.com and show build SHA in header.

APP_BASE_URL default (config, .env.example, both compose files) is now
https://conchecker.scoutitsystems.com with no port, so review-required
and final-report email links use the public site. CI bakes the short
commit SHA into the image as APP_BUILD via a Docker build-arg; /health
returns version+build and the site header shows the build so it's easy
to confirm which image is deployed. Local runs default to 'dev'.

backend/.env.example

@@ -45,7 +45,8 @@ EXTRACT_CONCURRENCY=4
 REASON_CONCURRENCY=4
 
 # Public URL users reach this server on (used for the link in result emails)
-APP_BASE_URL=http://localhost:8099
+APP_BASE_URL=https://conchecker.scoutitsystems.com
+# APP_BUILD is set by CI at image build time (sha-<short_sha>) - do not set manually.
 
 # Email notifications (optional). Leave SMTP_HOST blank to disable.
 # Examples: