fix: keep SABR seek sliders interactive

[Priveetee]

Summary

• keep video and audio SABR seek controls interactive while a seek is pending
• let repeated long-distance seeks immediately supersede an older pending request
• keep the current frontend version unchanged for the TypeType 1.2.4 hotpatch

Production behavior

• the seek slider remains usable during SABR recovery
• repeated forward and backward seeks target the latest requested position
• the pending seek indicator remains visible without intercepting pointer input
• no environment or database change is required

Runtime verification

• beta revision e533fb52736aa1b6ca6e15171a5bfe1a8341de81
• Chromium, Firefox and WebKit completed four rapid long-distance seeks on separate videos
• each browser reached playback generation 4 and resumed from the final target

Tests

• 125 frontend tests
• Biome check
• production build
• git diff --check

Rollback

• previous stable frontend revision: 9f7492cd84f593a9985d6b9c3b2d3e81d1123e42
• previous stable image: ghcr.io/typetype-video/typetype@sha256:562834d8476f02d5d6f5df5a62e6827bed2a614de85c0c231fbb797f93b36b06