fix: allow original Instagram feed images in composer

[paulocastellano]

Summary

• Let Instagram Feed images set to Original pass the editor's aspect-ratio gate, keeping the source URL unchanged for publication.
• Keep the selected 1:1, 4:5, and 16:9 crop behavior. Other content types retain their existing media checks.
• Render the Original preview at the source image's aspect ratio instead of a square.
• Cover a five-image 3:4 carousel in the browser: Original and 4:5 have no warning and allow submission; Original previews at 3:4.

Platform limitation

Meta's current media endpoint reference documents 4:5–1.91:1 for API-published images. This PR permits the unchanged 3:4 image to reach Meta; it does not establish that Meta will accept or publish it. The API may reject the container.

Verification

• php artisan test --compact tests/Browser/ChannelMediaIssueTest.php — 3 passed, 19 assertions in the primary checkout.
• npm run build and vue-tsc --noEmit — passed on the updated PR branch.
• vendor/bin/pint --dirty --format agent and git diff --check — passed.
• The browser test cannot start in the managed worktree because its symlinked vendor path is not recognized by the browser runner (__markAsBrowserTest reflection error); it passed in the primary checkout with the same edited files.