feat: prepare frontend 1.2.0

[Priveetee]

Summary

• load subscription feeds progressively
• update the MSE runtime to 0.1.38
• preserve saved progress and volume state during playback transitions
• forward repeated SABR seeks immediately
• add playback speeds up to 4x

Production behavior

• the first subscription videos can render before the complete feed finishes
• normal seeks and SponsorBlock skips reuse the current playback session
• temporary media transitions no longer overwrite the saved volume
• mobile MSE, Picture-in-Picture and buffered seeks use the current Player runtime

Runtime verification

• beta revision 0fc5311d5196e0474cc05115fdfdba155a7e965b
• validated VOD playback, repeated seeks, SponsorBlock, livestream playback and codec changes on beta
• @typetype/mse@0.1.38 is published and pinned by this revision

Tests

• bun run check
• bun run test:coverage
• bun run build
• bun run knip
• bun run sherif
• git diff --check
• Coverage and Docker workflows