chore(web): basic widget page

[KaWaite]

What I've done

Basic widget page UI with SOME functionality. You can add widgets and see them in the visualizer, select a widget.
Also some UI and code improvements that maybe should have gone in other PRs. Apologies

What I haven't done

Still can't edit or remove widgets. Can't see and edit fields on the selected widget

How I tested

Which point I want you to review particularly

Memo

[netlify]

✅ Deploy Preview for reearth-web ready!

Name	Link
🔨 Latest commit	87e6ed9
🔍 Latest deploy log	https://app.netlify.com/sites/reearth-web/deploys/64ba42a05e2cb40008385851
😎 Deploy Preview	https://deploy-preview-578--reearth-web.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[codecov]

Codecov Report

Merging #578 (87e6ed9) into main (53bf82f) will decrease coverage by 0.06%.
The diff coverage is 20.23%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #578      +/-   ##
==========================================
- Coverage   28.44%   28.38%   -0.06%     
==========================================
  Files        1401     1414      +13     
  Lines      150961   152092    +1131     
  Branches     3626     3636      +10     
==========================================
+ Hits        42943    43177     +234     
- Misses     106866   107763     +897     
  Partials     1152     1152              

Flag	Coverage Δ
web	26.29% <20.23%> (-0.06%)	⬇️
web-beta	26.29% <20.23%> (-0.06%)	⬇️
web-classic	26.29% <20.23%> (-0.06%)	⬇️
web-utils	26.29% <20.23%> (-0.06%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
server/internal/infrastructure/mongo/dataset.go	0.00% <ø> (ø)
server/internal/infrastructure/mongo/layer.go	7.05% <ø> (ø)
web/src/beta/components/Dropdown/index.tsx	0.00% <0.00%> (ø)
web/src/beta/components/ListItem/index.tsx	0.00% <0.00%> (ø)
...eb/src/beta/components/properties/Toggle/index.tsx	0.00% <0.00%> (ø)
...eb/src/beta/features/Editor/SecondaryNav/index.tsx	0.00% <0.00%> (ø)
web/src/beta/features/Editor/SidePanel/index.tsx	0.00% <0.00%> (ø)
...a/features/Editor/Visualizer/CanvasArea/convert.ts	0.00% <0.00%> (ø)
...eta/features/Editor/Visualizer/CanvasArea/hooks.ts	0.00% <0.00%> (ø)
...ta/features/Editor/Visualizer/CanvasArea/index.tsx	0.00% <0.00%> (ø)
... and 35 more