[INTEG-3768] fix: resolve asset references and upload images via OAuth fetch

[ryunsong-contentful]

Purpose

• Contentful's servers can't access Google's signed image URLs — fixed by fetching the binary in the browser and uploading it directly to Contentful
• Asset placeholder IDs were only being resolved in RichText fields, not standalone Media fields — fixed by extending the resolution to all asset field types
• Lookup misses if the agent encoded the URL differently — fixed by storing both raw and normalised URLs as keys, and omitting the field entirely if the placeholder still can't be resolved (instead of writing a broken reference)

To view the how these changes performed see the latest entries created in https://app.contentful.com/spaces/9pm311s1i5qt/environments/franco-fe-entries-creation/views/entries