…splay

Backend optimizations:
- Refactor get_random_images() using SQLite ORDER BY RANDOM()
- Simplify from 60+ lines to ~20 lines with better performance
- Remove complex multi-cycle index calculations
- Maintain file existence check and auto-cleanup

ComfyUI support:
- Add fallback to 'parameters' field in PNG metadata
- Improve detection for ComfyUI-generated images

Frontend improvements:
- Smart prompt display: auto-detect tag vs natural language format
- Add getTextLength() with Chinese character weight (1 char = 3 letters)
- Refactor isTagStylePrompt() with clear rules:
  * Any tag length > 50  natural language format
  * Average tag length > 30  natural language format
- Natural language prompts shown as paragraphs
- Tag-style prompts shown as badges
- Better support for Chinese/English mixed content

Build:
- Update frontend asset references