Docs: Add comprehensive documentation for missing features

Document previously undocumented features:
- ManagerRegistry::reopen() static method for reopening closed EntityManagers
- resolveTargetEntities configuration for interface-based entity architecture
- Custom DQL functions (string, numeric, datetime) with examples
- Custom hydration modes with implementation example
- Filters configuration with enable/disable and runtime management
- Events system with auto-discovered event subscribers
- Customization options: naming strategy, quote strategy, repository factory, entity listener resolver
- Default query hints configuration
- Multiple connections and managers setup with usage examples

Update table of contents to include all new sections.

Author: claude