Release v15.16.0

What's New

• Save as PDF: every saved page gets a table-of-contents (outline) entry, and pages can be appended to an existing PDF — collect articles into one document with a navigable TOC (great on e-ink readers like Supernote)
• Faster startup: tabs restore lazily with persisted titles
• GPT settings reorganized into a hub with per-provider sub-pages
• Userscript UI: browse-scripts link and quick access to settings
• Volume-key page-turn toggle in gesture settings
• Side-by-side test build (info.plateaukao.einkbro.a) attached to releases

Bug Fixes

• Settings screen stays in the browser task instead of opening a separate one (#612)
• Backup/Restore works across application ids, so the .a build can share data
• Offline error page: reload re-fetches the real URL and auto-recovers; connectivity polling removed to save battery
• Toolbar clock no longer ellipsizes in vertical mode