feat: prepare token 1.6.0

[Priveetee]

Summary

• mint account-bound YouTube SABR token pairs
• preserve the selected connected YouTube account through token refresh
• complete the internal Token service mock contract
• prepare Token version 1.6.0

Production behavior

Server can request player and media tokens bound to the selected YouTube account instead of falling back to an anonymous session. Public Token routes and configuration remain unchanged.

Tests

• bun install --frozen-lockfile
• bun test
• bun run lint
• bun run build
• git diff --check

Rollback

Restore Token revision 83371ef0.