feat: apply Decizyon brand identity

[davibritovilela52-design]

Summary

• add Decizyon brand assets and metadata
• update sidebar/auth/header branding and default theme
• make locale-sensitive tests portable and ignore local tool artifacts

Validation

• npm test
• npm run typecheck
• npm run build

[ArnasDon]

Closing this one — it's a rebrand of the upstream template, so it's not something upstream can merge.

The diff renames the project to Decizyon CRM in layout.tsx metadata, points the icons at /brand/decizyon-icon.png, adds a decizyon theme and makes it DEFAULT_THEME. That's exactly the customisation step CONTRIBUTING.md describes — "Customise your fork. Rebrand, add the features you need" — and it belongs on your fork, where it already lives.

Nothing to fix here; just closing so the queue reflects what's actually pending. Good luck with Decizyon.