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/it/translation.json

@@ -54,6 +54,8 @@
   "Delete expression": "Elimina espressione",
   "Delete filter block": "Elimina blocco filtro",
   "Deuteranopia filter": "Filtro deuteranopia",
+  "Drag to resize the layer list": "Trascina per ridimensionare l'elenco dei livelli",
+  "Drag to resize the sidebar": "Trascina per ridimensionare la barra laterale",
   "Duplicate": "Duplica",
   "Encoding": "Codifica",
   "Enter URL...": "Inserisci URL...",