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

[pthmas]

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 <pre> 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'