Prepare GLTFQuickLook 1.1.0 beta

[hectorlizard]

Summary

• publish the validated sidecar cache, Unreal material, Sketchfab, and oversized animation compatibility work
• retain the first 10 animations for exceptional uModel character exports
• use the native Quick Look background in Light and Dark Mode
• document the ad hoc signed installation and Gatekeeper fallback

Release engineering

• bump all modern bundles to 1.1.0 (build 2)
• pin GLTFSceneKit to the validated revision
• add sandbox-only release entitlements without get-task-allow
• add CI, release packaging, checksum, changelog, security policy, and privacy hygiene checks
• preserve the current preview animation from master

Validation

• local clean Release build and ZIP round-trip signature verification passed
• app and both extensions are arm64 and ad hoc signed
• both extensions retain the macOS app sandbox entitlement
• no build-machine paths or personal identifiers were found in tracked history or shipped binaries
• GitHub CI passed on the release branch

Merging this PR does not publish a binary. Pushing tag v1.1.0-beta.1 will trigger the release workflow and create the prerelease assets.