feat(docs): establish Blume documentation site (#35)

## Summary

Establishes DomainKit's Blume documentation app and a Cloudflare Workers
Static Assets deployment target for `domain-kit.dev`.

## Configuration

```ts
export default defineConfig({
  deployment: {
    output: "static",
    site: "https://domain-kit.dev",
  },
  search: { provider: "orama" },
});
```

## Screenshots

![DomainKit docs landing
page](https://scratchpad.arya.sh/f/01a05281-f725-7bb2-b130-37166076a062/domainkit-docs-foundation.png)

## Validation

- `bun run docs:build`
- `bun run --filter @domainkit/docs typecheck`
- `bun run docs:audit` (228 audits, 0 findings)
- `bun run lint`
- `bun run format:check`
- `bunx wrangler deploy --dry-run --config apps/docs/wrangler.jsonc`
- Browser review of the generated landing page and navigation

## Follow-up scope

- SDK and React guides are stacked separately.
- Cloudflare AI Search remains a post-deployment follow-up; this layer
uses Blume's local Orama index.