feat: migrate image tools to Next.js

[rossgalloway]

Summary

• migrate the image upload tool from Vite and Vercel Functions to Next.js 16 App Router route handlers
• preserve token and chain uploads, GitHub OAuth preview returns, repository targeting, and automatic chain path creation
• harden chain ID validation and OAuth callback state handling
• update the header with the Yearn tokenAssets GitHub link and revised sign-in styling

Why

This change keeps the framework (nextJS) consistent with the yearn.fi site, which recently switched from Vite to nextJS.

Impact and risk

• This is a full overhaul of the website framework so we should confirm all is working correctly.
• image-tools now runs with next dev, next build, and next start

Validation

• bun test — 25 passing
• bun run typecheck
• bun run build
• conflict-free merge tree against current origin/main

[vercel]

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Project	Deployment	Actions	Updated (UTC)
token-assets	Ready	Preview, Comment	Jul 16, 2026 4:02pm
token-assets-ui	Error		Jul 16, 2026 4:02pm