v3.1.0

• thumbnails: rewrite to async
• thumbnails: removed dependence ImageMagick and md5
• api/post_file: rewrite to async
• api/get_all: rewrite to async
• File implementation
• new index4.js
• codemirror bundle update cm6.bundle-20250710.min.js

codemirror:

• disable autocomplete
• disable black theme
• add highlight JSON

editors:

• open SH as CODE
• for new SH file - open CODE online editor
• for new JSON file - open CODE online editor
• for new MD file - open in MARKDOWN editor
• fix: ability to save EMPTY source code file