fix(github): plumb GITHUB_APP_SLUG / GITHUB_WEBHOOK_SECRET through self-host

The GitHub App integration code reads these two env vars and only enables
the Connect flow when both are set. .env.example never listed them, and
docker-compose.selfhost.yml did not forward them into the backend
container, so self-hosters following the integration docs had no working
way to turn the feature on.

MUL-2107

Co-authored-by: multica-agent <github@multica.ai>

.env.example

@@ -101,6 +101,13 @@ ALLOWED_ORIGINS=
 # `Authorization: Bearer <token>`.
 # REALTIME_METRICS_TOKEN=
 
+# GitHub App integration (Settings → Integrations "Connect GitHub")
+# Both must be set for the Connect button to enable and for webhooks to be
+# accepted; leave empty to disable the integration. See docs/github-integration.
+# GITHUB_APP_SLUG is the tail of https://github.com/apps/<slug>.
+GITHUB_APP_SLUG=
+GITHUB_WEBHOOK_SECRET=
+
 # Frontend
 FRONTEND_PORT=3000
 FRONTEND_ORIGIN=http://localhost:3000

docker-compose.selfhost.yml

@@ -58,9 +58,11 @@ services:
       APP_ENV: ${APP_ENV:-production}
       MULTICA_DEV_VERIFICATION_CODE: ${MULTICA_DEV_VERIFICATION_CODE:-}
       MULTICA_APP_URL: ${MULTICA_APP_URL:-http://localhost:3000}
-      ALLOW_SIGNUP: ${ALLOW_SIGNUP:-true}                                     
-      ALLOWED_EMAILS: ${ALLOWED_EMAILS:-}                                     
-      ALLOWED_EMAIL_DOMAINS: ${ALLOWED_EMAIL_DOMAINS:-} 
+      ALLOW_SIGNUP: ${ALLOW_SIGNUP:-true}
+      ALLOWED_EMAILS: ${ALLOWED_EMAILS:-}
+      ALLOWED_EMAIL_DOMAINS: ${ALLOWED_EMAIL_DOMAINS:-}
+      GITHUB_APP_SLUG: ${GITHUB_APP_SLUG:-}
+      GITHUB_WEBHOOK_SECRET: ${GITHUB_WEBHOOK_SECRET:-}
     restart: unless-stopped
 
   frontend: