fix(deploynotify): preserve coolify source commit

.env.example

@@ -24,11 +24,9 @@ ADMIN_IDS=
 GEMINI_API_KEY=
 
 # SOURCE_COMMIT (commit SHA) is read at startup for the deploynotify owner DM.
-# Do NOT set it here. On Coolify (Docker Compose) it is a predefined variable
-# that reaches the container only because compose.yml references it
-# (`SOURCE_COMMIT: ${SOURCE_COMMIT:-}`) — Coolify supplies the value via
-# --env-file. Local `docker compose up` has none, so deploynotify reports
-# "unknown".
+# Do NOT set it here. Coolify provides it at runtime. Keep "Include Source
+# Commit in Build" disabled so Docker layer cache survives across commits.
+# Local `docker compose up` has none, so deploynotify reports "unknown".
 
 # ====================== Leave UNSET on self-host ==================
 # Defaults are correct for self-host: