Replaces the custom Go/Vue notes system with Quartz v4, a polished
static site generator for Obsidian vaults. Mounts OBSIDIAN_DIR as the
Quartz content directory and serves it at /notes/ with hot-reload via
`npx quartz build --serve`.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
