feat(content): preview explicitly reviewed collection HTML settings

[mysbryce]

Owners can explicitly review collection HTML settings, select that saved snapshot and generate private HTML. A concurrent settings change blocks generation until reviewed again. Temporary settings and the separate settings editor keep their authored values.

The strict owner HTTP boundary checks the exact renderer revision alongside the saved entry and frozen model. Preview reads change neither content, settings nor audit. Seven languages use custom controls; pending operations retain authority and navigation guards. This delivery previews private content; canonical CMS publication follows separately.

Validation:

• Full core: types, 408 backend cases/9,149 assertions, build and formatting. All 73 browser cases pass.
• Portuguese badge overflow passed its own public RED/GREEN repair. Final types, fresh build, whole formatting and release policy pass after the two badge classes; full core/browser receipts precede those classes.
• Final gallery: 1,319 PNGs/49 receipts, preserving all 1,305 prior canonical metadata records. Original review of 14 new and six affected legacy images matches promoted hashes. The initial blank-frame capture was rejected and corrected with visible-viewport capture.
• Fresh compiled portable: ten cases/1,156 assertions, actual saved and temporary HTML previews, unchanged public snapshots. All ten portable originals reviewed.
• Exact executable/input hashes and unchanged notice scopes verified. Clean committed source bundle: 1,044 files/24,285,714 bytes, matching source/payload hashes.
• Version 0.26.0-alpha.0, changelog, guides and roadmap updated. All three exact-head CI jobs pass at reviewed head bb8171c939dcbc5fbf6a6c9d10f124b419ec3c16.

No new tag, public executable or deployment. Scoped screenshots do not establish native-speaker certification or production capacity.