Central video library: reuse a recorded video across page templates, workflows and sequences

Customer request (raised via support conversation with Lennart Øster, 2026-08-25): Today a video recorded in one context (e.g. a mail flow) cannot be reused elsewhere (e.g. a landing page template) without re-recording from scratch. The customer built a video for a mail flow, then needed the same video on a landing page template and found no way to move or attach it there, forcing a full re-record. Requested: a video library/asset store where a video recorded once can be selected and attached to any template, workflow, or automation, instead of being tied to the single context it was recorded in. Impact: significant time cost and friction any time a template, workflow, or automation changes and reuses the same base video. Directly cited as a reason the customer considered leaving. Related but distinct from the existing "Re-use lipsync videos" request (reusing a lipsync render for repeated first-name contacts within one campaign) — this request is about reusing one base video asset across different templates/workflows/campaigns.