feat: port to TYPO3 v14 (v2.0.0)

[morri5]

Summary

• Drop TYPO3 v11/v12/v13 support, require v14 and PHP 8.2+
• Replace removed APIs: FileType enum, IconSize enum, ViewFactoryInterface, Fluid 5 render(), no-arg AbstractProvider constructor
• Add system prompt with persistence, protection, and restore defaults
• Add cancel button and progress bar improvements for Generate All
• Add X-AIGUDE-Client header for Prometheus metrics
• Fix default prompt pre-selection in dropdown
• Collapsible placeholder/modifier panels in prompt editor
• Fix picomatch CVE-2026-33671
• Standalone MetaDataRepository (parent is readonly in v14)
• Remove t3_origuid column usage (dropped in v14)

Version strategy

• 1.x branch created to preserve v11-v13 support
• master becomes v2.x for TYPO3 v14+
• Packagist resolves the right version automatically based on TYPO3 constraints

Test plan

• Extension installs via Composer on TYPO3 v14
• Backend modules load (Prompts, Settings)
• Context menu shows "Generate A.I. Metadata" on image files
• Generate All with cancel button and progress bar
• System prompt persists, cannot be deleted, can be restored
• Multi-language translation works
• No deprecation warnings