List Recent Videos

Recent summarized videos with titles, for the frontend to build human-readable link hubs (/videos/ids returns bare ids, useless for link text). Public, unauthenticated. channel (exact name) backs the frontend's channel pages and same-channel links; tag (a summary's category tag, case-insensitive) backs the library's tag filter. lang is the reader's language: titles come from the summary in that language when one exists (else English, else YouTube's). Reads never generate translations. Declared ABOVE /videos/{video_id} — same Starlette route-ordering requirement as /videos/ids: the literal recent path segment must be matched here first, otherwise it would be captured by {video_id} and auth-gated.