Chrome extension and dashboard rebuild

Rebuilt Chrome extension with redesigned sidebar, smarter cloud sync, themes, and four keyboard shortcuts
In-extension PDF viewer for online PDFs; dashboard upload flow for local and cloud-stored PDFs
Web dashboard library with advanced search, hierarchical labels, PDF upload and annotation, overview analytics, trash, and bulk export
Post-update welcome page at /whats-new for users upgrading from extension v7.x
One-time account migration flow with 7-day Pro trial for legacy cloud users

Sync reliability with debounced auto-sync, retry logic, and clearer conflict and subscription messages
Local pages manager with sync status badges, filters, and storage usage monitoring
15-language UI across extension, dashboard, and documentation

Local file:// PDFs no longer open directly in the extension — upload via the dashboard instead
Unified sidebar replaces the old floating-toolbar mode
Cloud features require an active Pro trial or subscription

Extension update detection — persistent toast prompts users to refresh open tabs after an update