fix: Slowness in deleting big number of items

[arabcoders]

This pull request introduces a new bulk deletion feature for download history items, enhances the status filtering capabilities for deletions, and adds a new API endpoint to retrieve system limits. It also introduces a new notification event for bulk deletions and improves the documentation to reflect these changes. Some minor config and code cleanups are also included.

Bulk Deletion and Status Filtering Enhancements

• Added support for bulk deletion of history items by explicit IDs or by advanced status filters (including comma-separated include/exclude filters like "finished,skip" or "!finished,!skip"). This includes both backend logic and API documentation updates. [1] [2] [3] [4] [5] [6] [7] [8]
• Added a new notification event item_bulk_deleted to signal when multiple items are deleted in a single operation, with accompanying schema and frontend registration. [1] [2] [3] [4] [5]

API Improvements

• Introduced a new API endpoint GET /api/system/limits for retrieving current system and download limits, with detailed response documentation. [1] [2]

Documentation and Config Cleanups

• Updated API documentation to describe new endpoints, events, and usage examples for bulk deletion and status filtering. [1] [2] [3] [4] [5] [6] [7]
• Removed the unused ui_update_title config option and renamed prevent_premiere_live to prevent_live_premiere for consistency. [1] [2] [3] [4]

Miscellaneous

• Made the premiere buffer time for live videos configurable, using the new config value in video processing.
• Minor code improvements and refactoring in SQLite store utilities. [1] [2] [3]