feat(backend): Add user profile

[matmair]

This PR:

• Adds user profiles containing basic info needed for commercial ops
• Enables persisting of preferred language
• Enables persisting of theme settings
• Enables persisting of widgets
• Adds user and group info pages

Closes invenhost#107
Closes invenhost#93
Closes invenhost#117

[netlify]

✅ Deploy Preview for inventree-web-pui-preview ready!

Name	Link
🔨 Latest commit	29f56d8
🔍 Latest deploy log	https://app.netlify.com/sites/inventree-web-pui-preview/deploys/67b9a5797e2ac50008bfdce5
😎 Deploy Preview	https://deploy-preview-9116--inventree-web-pui-preview.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.
Lighthouse	1 paths audited Performance: 96 (no change from production) Accessibility: 89 (no change from production) Best Practices: 92 (no change from production) SEO: 78 (no change from production) PWA: - View the detailed breakdown and full score reports

---

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

[codecov]

Codecov Report

Attention: Patch coverage is 95.70552% with 7 lines in your changes missing coverage. Please review.

Project coverage is 86.16%. Comparing base (2cabd02) to head (29f56d8).

Files with missing lines	Patch %	Lines
src/backend/InvenTree/users/models.py	86.27%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #9116      +/-   ##
==========================================
+ Coverage   86.09%   86.16%   +0.06%     
==========================================
  Files        1179     1180       +1     
  Lines       52095    52215     +120     
  Branches     2173     2174       +1     
==========================================
+ Hits        44852    44989     +137     
+ Misses       6684     6665      -19     
- Partials      559      561       +2     

Flag	Coverage Δ
backend	88.10% <87.16%> (+<0.01%)	⬆️
migrations	43.00% <50.67%> (+0.04%)	⬆️
pui	69.49% <100.00%> (+0.08%)	⬆️

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.