Replace Google Fonts with `next/font` (already done) + ensure font subsetting is regionally optimal

[snowrugar-beep]

• Problem Statement. app/layout.tsx imports Geist, Geist_Mono
  via next/font/google. Some visitors might benefit from regional
  subsetting (Noto Sans CJK etc.).
• Why it matters. Fonts easily bloat the LCP payload.
• Expected Outcome. Each route declares the locales it serves;
  font files are subset by unicode-range.
• Acceptance Criteria.
  1. app/page.tsx declares preloads.
  2. Network panel shows reduced subset for users with non-Latin
     systems.
• Files / Modules. Frontend/src/app/layout.tsx.
• Difficulty. Easy.
• Effort. 0.5 day.
• Labels. frontend, performance, i18n.

[darius-daniel]

I'd like to work on this issue.

I'll optimize font loading by configuring locale-aware font subsetting in app/layout.tsx, ensuring only the required glyph ranges are loaded for each route. I'll verify that the appropriate font subsets are preloaded, reduce unnecessary font payloads, and confirm the improvements through network inspection and performance validation.

[grantfox-oss]

🦊 GrantFox — @darius-daniel has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #148)
2. Your PR will be reviewed by the VertexChainLabs maintainers

Good luck! Track your progress on GrantFox.