Upgrade to Bootstrap v5 and add dark mode support

[Amdrel]

Affected Components: frontend, socket.io

Description

Resolves #331

This patch migrates the frontend to Bootstrap v5 and upgrades all other dependencies to the maximum versions possible taking compatibility into account. I've tested this patch a bit (including RTL) in both light and dark mode.

The application looks a bit more "modern" since Bootstrap 5 has different base styles than 3, however everything is still positioned in the same places as before.

Library Version Changes

• Frontend library upgrades
  • Add Bootstrap Icons 1.13.1 (replacing Glyphicons bundled with Bootstrap 3)
  • Upgrade Bootstrap from 3.3.6 to 5.3.8
  • Upgrade jQuery from 2.2.0 to 3.7.1
  • Upgrade GitHub Fork Ribbon CSS from 0.1.1 to 0.2.3
• Frontend build library upgrades
  • Upgrade Biome from 2.3.13 to ^2.4.8
  • Upgrade gulp-htmlmin from >3.0.0 to ^5.0.1
  • Upgrade gulp-nunjucks from >3.1.1 to ^6.1.0
  • Upgrade gulp-rename from >1.4.0 to ^2.1.0
  • Upgrade gulp-uglify from >2.1.2 to ^3.0.2
• Socket.io app library upgrades
  • Upgrade Express from ^4.21.1 to ^5.2.1
  • Upgrade Redis (Node.js) from ^4.6.12 to ^5.11.0
  • Upgrade Socket.io from ^4.8.0 to ^4.8.3
• Python library upgrades
  • Upgrade Ruff from 0.14.14 to 0.15.7

Code Changes

• Added dark mode toggle to the site header when logged in
  • Defaults to the system theme
  • The user's preference is saved to localstorage
• Refactored classes exclusive to Bootstrap 3 & 4 to Bootstrap 5 variants
• Made a path fix to the socket.io app since Express broke glob * (why?)

Screenshots

Task list with dark mode applied

Add task dialog with dark mode applied

Target page with dark mode applied (labels have more bottom margin in final version)

Screenshot demonstrating that light mode still works

RTL support still working in Bootstrap 5 with Hebrew

Playlist dialog with updated styles

[don-vip]

@Amdrel very nice! I see CI/Biome raised two warnings in video2commons.js, is it possible to resolve them?

[Amdrel]

Done. I also modified the workflow to clean up broken symlinks before the lint check. Those are needed by the application but biome seems to dislike them.