Upgrade to Next.js 16 and next-intl 4.9.1

[JohnRDOrazio]

Summary

Upgrade from Next.js 15.5.14 to 16.2.4, and next-intl from 4.1.0 to 4.9.1. This resolves an intermittent Cannot read properties of undefined (reading 'payload') console error during page loads caused by a known RSC flight data issue in Next.js 15.x.

Changes Required

• middleware.ts → proxy.ts: Next.js 16 renames middleware to proxy with a named export
• revalidateTag() signature: Now requires a second argument (cache lifetime profile)
• ESLint flat config: next lint command removed; migrate to eslint.config.mjs with ESLint CLI
• Dependency bumps: next, next-intl, react, react-dom, eslint-config-next, @types/react, @types/react-dom

Lint Fixes (pre-existing)

The stricter React 19.2 and TypeScript ESLint rules surfaced several pre-existing issues:

• react-hooks/refs: Reading refs during render in 3 modal components → converted to state
• react-hooks/set-state-in-effect: Unnecessary setState calls in effects → derived values / lazy initializers
• react-hooks/purity: Impure Math.random in render → lazy useState initializer
• @typescript-eslint/no-explicit-any: as any locale casts → as readonly string[]
• @next/next/no-img-element: <img> for logo → next/image

Testing

• npm run build passes
• npm run lint passes clean (0 errors, 0 warnings)
• npm run dev starts successfully on Next.js 16.2.4 (Turbopack)
• All pages render correctly
• Form modals (Submit Project, Refer Community Project, Refer Local Group) work correctly with state-based form data
• Share buttons work on blog/project pages