feat: make sidebar panels resizable (#2094)

- Replaces #1870, which replaced #1682, #1677

This mostly uses the code from there and addresses the comments I've
left. I didn't change the code much.

## Launch Checklist

Makes the sidebar panel resizable

<img width="707" height="511" alt="image"
src="https://github.com/user-attachments/assets/d010df38-faac-441c-bf7f-a4960e471c61"
/>


 - [x] Briefly describe the changes in this PR.
 - [x] Link to related issues.
- [x] Include before/after visuals or gifs if this PR includes visual
changes.
 - [x] Write tests for all new functionality.
 - [x] Add an entry to `CHANGELOG.md` under the `## main` section.

---------

Co-authored-by: Bart Louwers <bart.louwers@gmail.com>

src/locales/ko/translation.json

@@ -54,6 +54,8 @@
   "Delete expression": "표현식 삭제",
   "Delete filter block": "필터 블록 삭제",
   "Deuteranopia filter": "녹색맹 필터",
+  "Drag to resize the layer list": "드래그하여 레이어 목록 크기 조정",
+  "Drag to resize the sidebar": "드래그하여 사이드바 크기 조정",
   "Duplicate": "복제",
   "Encoding": "인코딩",
   "Enter URL...": "URL 입력...",