fix(useStrapiMedia): use public URL during server rendering

[BayBreezy]

Types of changes

• Bug fix (a non-breaking change which fixes an issue)
• New feature (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Description

With separate internal and public Strapi URLs, generated pages can contain localhost media URLs. useStrapiMedia selected the private URL during server rendering. It now resolves relative media paths against the public URL consistently, so SSR and generated pages emit browser-accessible media URLs. Absolute URLs remain unchanged. Fixes #388.

Verified: lint, typecheck, all 45 tests (including SSR and prerender regressions), and build.

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes (if not applicable, please state why)

[pkg-pr-new]

npm i https://pkg.pr.new/@nuxtjs/strapi@558

commit: 79f01c9