Search Enhancements:
- Added search history feature
- Added regex search mode toggle
- Added clear button to search input
- Added regex timeout and match limits to prevent catastrophic backtracking
- Fixed handling of non-existent tabs by falling back to new tab

Tab Management:
- Added auto-discard feature for inactive tabs
- Added tab preview toggle to settings
- Added page tagging system for tabs

Indexing & Database:
- Added indexed pages management UI with search and pagination
- Added lastIncrementalUpdate field to page index
- Fixed URL normalization for matching tabs during index updates
- Fixed URL keys to include query parameters for proper differentiation

Core Improvements:
- Added StateManager for centralized state management
- Added settings-manager.js to content scripts
- Optimized rendering and data persistence with batching and caching
- Added new search keyboard shortcut (Alt+F)