fix(ui): remove unused dropzone component and pixi deps

[Ansh-Sonkusare]

Fixes #1738

• Delete packages/ui/components/shadcn-io/dropzone.tsx. It imports react-dropzone, which was never a dependency, and nothing imports the component.
• Remove pixi.js and @pixi/react from packages/ui. Nothing imports them.

bun.lock is regenerated with bun install. Besides the pixi entries, bun also pruned some already-orphaned entries (e.g. @cloudflare/ai-chat, tsx, @ai-sdk/react@3) that no workspace declares. Main's lockfile doesn't change under a plain bun install, so these only go away when a dependency changes.

Before

$ cd packages/ui && bunx tsc --noEmit
components/shadcn-io/dropzone.tsx(8,64): error TS2307: Cannot find module 'react-dropzone' ...
(5 errors)

After

$ cd packages/ui && bunx tsc --noEmit    # exit 0
$ bun install --frozen-lockfile          # ok

In bun run check-types, @repo/ui now passes. Root still fails on @supermemory/tools test files; that's pre-existing and unrelated.