Fix build: generate settings.json from env vars at runtime

settings.json is gitignored (contains token). entrypoint.sh writes it
from OUTLINE_URL / OUTLINE_TOKEN env vars on container start.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

entrypoint.sh

@@ -0,0 +1,15 @@
+#!/bin/sh
+set -e
+
+# Generate settings.json from environment variables at container start.
+# OUTLINE_URL and OUTLINE_TOKEN must be set (e.g. via docker-compose env / .env file).
+
+cat > /work/settings.json <<EOF
+{
+  "source": { "url": "${OUTLINE_URL}", "token": "${OUTLINE_TOKEN}" },
+  "target": { "url": "${OUTLINE_URL}", "token": "${OUTLINE_TOKEN}" },
+  "sync":   { "allow_deletions": false }
+}
+EOF
+
+exec "$@"