[Proposal] `npx create-fedify-app`

### Summary

Implement `npx create-fedify-app`.

### Problem

- Install [`@fedify/cli`](https://github.com/fedify-dev/fedify/blob/main/packages/cli) globally.
- Execute `fedify init`.
- Install [`@fedify/fedify`](https://github.com/fedify-dev/fedify/blob/main/packages/fedify).
- etc...

### Proposed Solution

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### Alternatives Considered

_No response_

### Scope / Dependencies

_No response_