v0.1.18

Release v0.1.18: Notes sync diagnostics and cache hardening, manual push/pull controls, copyable sync logs, authoritative server pulls for browser Notes, and Files open actions for notes/audio/local files. Includes linux/amd64 server Docker artifact and signed Notes Android APK. APK icon hotfix: full black Android launcher background with a smaller white Notes mark and corrected adaptive/legacy launcher resources.