fix(frontend): vite 8 manualChunks must be a function; bump deps

Vite 8 (rolldown) rejects the object form of build.rollupOptions.output.manualChunks
with "manualChunks is not a function". Convert to the function form, preserving the
react/ui/auth vendor chunks. Bump vite to 8.1.0 and apply in-range dependency updates.

Author: razkenari