v0.7.6

Added

• PageFile::isPublic() and PageFiles::isPublic().
• PageFiles::makePrivate() withdraws a file: it forgets every URL the file was exposed at and wipes its mirror and cached variants. PageFiles::delete() uses it.
• A variants_owner index on (page_uuid, original) in the variants table.

Changed

• The public flag is no longer stored in {filename}.index.json or passed to PageFile. PageFile::url() records the file's own URL as a variants row with no options, the same table image variants use, and the file is public exactly when a row names it.
• PageFiles::serveFrom() serves whatever the request path was recorded as: a rendered variant, or the stored file when the row has no options. A private file still 404s when it exists on disk.