Migrate to oxlint, oxfmt, and rolldown-vite for faster builds

[plebe1us]

The current tooling setup uses ESLint for linting, Prettier for formatting, and standard Vite (esbuild + Rollup) for bundling. These can be replaced with faster Rust/Go-based alternatives from the oxc project and VoidZero.

Proposed changes:

• Replace ESLint with oxlint (50-100x faster linting)
• Replace Prettier with oxfmt (35x faster formatting)
• Replace Vite with rolldown-vite (3-16x faster builds)

Why rolldown-vite is suitable for Seedit despite being experimental:

• Seedit is a fully static SPA with no SSR — the simplest and lowest-risk use case
• Build output is just static files that can be easily verified before deploying
• The worst-case scenario is a failed build, not production runtime issues
• Easy rollback by reverting the package.json resolution

Expected benefits:

• Significantly faster CI builds
• Faster local development feedback loop
• Reduced dev dependency count (removes 6+ ESLint packages)
• Future-proofing as these tools become the standard (rolldown will be in Vite 8)