The Laravel and WordPress adapters pass their disk config straight to the
core DiskManager/FileManager, which read `endpoint`, `visibility` and
`public_url` — but neither adapter surfaced those keys, so the
S3-compatible (MinIO/Spaces), public-disk and CDN/public_url flows were
silently unreachable through the adapters (always private, native-AWS).

- laravel config/fluxfiles.php: s3 gains AWS_ENDPOINT/AWS_VISIBILITY/
  AWS_PUBLIC_URL; r2 gains R2_VISIBILITY/R2_PUBLIC_URL. README documents
  the cloud-storage env vars.
- wordpress: diskConfigs() reads the matching options (fluxfiles_s3_endpoint
  /_visibility/_public_url, fluxfiles_r2_visibility/_public_url), with new
  admin fields + register_setting so they're settable from Settings.
- wordpress smoke covers the defaults + the MinIO/public flow.

Node BYOB config already exposed these; react/vue/sdk are client-only
(token + endpoint), so no disk-config gap there.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>