fix: correct /data API usage and data format for importing share URLs

[yuvrajvirk]

Fixes opencode import failing for valid share URLs which currently return “Not Found” despite being publicly accessible.

Fixes

• Fetch share data from the correct endpoint: /api/share/:id/data
• Use ShareNext.url() instead of hardcoding url
• Transform data returned by API into structure expected for local storage
• Add unit tests demonstrating expected behavior for URL parsing and data transformation for local storage

Fixes #7106