Video gallery used by /videos.

<br/>Scoped to the caller's own videos, admins included (default-own<br/>scoping, spec §3.5, 2026-08-11). Owner, avatar, and search filtering,<br/>the seven chip counts, and the page slice all happen in SQL<br/>(repository.list_gallery), so a request costs O(page), not O(the<br/>caller's videos). The counts and total still describe the full<br/>filtered set; has_more tells the client whether to fetch the next<br/>page, and a page past the end echoes the requested page number.<br/><br/>Backwards compat: when the legacy limit is set (1 to 100, same<br/>bounds as page_size), it means page 1 of size limit.