feat: show full NFT metadata fields with raw JSON toggle on token page

## Problem

NFT token page only surfaces image, description, and attributes. All other metadata fields (custom properties, rarity scores, external_url, animation_url, etc.) are silently ignored. No way to inspect raw metadata JSON.

## Proposed Solution

Add a **Metadata** section below the attributes card on the NFT token page with two modes:

### Formatted view (default)
- Render every key/value pair from `token.metadata` dynamically
- Skip already-displayed fields: `image`, `image_url`, `imageUrl`, `image_data`, `description`, `attributes`
- Format values: strings as text, numbers as monospace, URLs as anchor links, objects/arrays as pretty-printed JSON blocks
- Section header: "Metadata" with a toggle button

### Raw JSON view (toggle)
- Switch button (e.g. "Formatted / Raw") in the section header
- Renders `JSON.stringify(token.metadata, null, 2)` in a scrollable `

` block with monospace font


### UX details

- Toggle state: `useState` local, default to formatted

- Only show section when `token.metadata !== null`

- Hide section when `metadata_status !== 'fetched'`