File visibility from published usage + reliable file deletion

[jirkamotejl]

What

• Folio::File#used_in_published_content? — live check whether a file is used in at least one published piece of content. Unwraps atoms to their parent record, respects the owner's published? (incl. published_at), ignores orphaned placements, counts owners without a publish concept as published. Early-exit batched iteration; single-record use only (collections need an SQL scope). Intended for host apps that derive public visibility of standalone file pages (e.g. video detail) from usage.
• Reliable deletion — a stale file_placements_count no longer blocks file destroy. New Folio::File#live_indestructible_reason re-verifies the placements message with a live query; used by the model destroy guard, the console file detail and the API destroy. File lists keep the cheap counter. Host-app indestructible_reason overrides keep working (non-placements reasons pass through).
• Console usage list — orphaned placements (owner deleted) are now rendered with the option to remove them (new orphan-only destroy endpoint, authorized via the file, fail-closed) instead of being silently skipped while blocking deletion. Each row shows a published/unpublished badge of the owning record. The usage section auto-expands when deletion is blocked.
• Rake tasks — folio:files:recalculate_placement_counts (counter drift fix, DRY_RUN/ALL_VIDEOS) and folio:files:report_videos_without_published_usage (CSV report).
• Tests pin the existing FriendlyId slug history cleanup (dependent: :destroy from friendly_id) and CRA media cleanup job enqueue on destroy — no behavior change there.

Notes

• calculate_published_usage_count / published_usage_count semantics are intentionally unchanged (consumed by usage-limit licensing) — the new visibility check is a separate, documented measure.

Tests

Model, controller (console + API) and component tests included; suites green.