[Tlaster]

Weibo's native timeline groups were unavailable as selectable sources. Add existing custom follow groups, Friends Circle, and Private Following to Add timeline, so users can pin each source to Home or include it in a mixed timeline. Friends Circle and Private Following also appear as per-account sidebar shortcuts.

Use one feed loader for the dedicated group/circle/private endpoints, with the existing Cookie session, account proxy, status rendering, and max_id pagination. Preserve existing custom-group configuration and cache keys, and isolate the two new feeds by account/source. Add English and Simplified/Traditional Chinese titles to all platform mappings.

Refs #2676 (native timeline groups).

Validation:

• 63 Weibo JVM tests passed, including 16 group/feed regressions covering routing, authentication, paging, cancellation, cache identity, and ProtoBuf persistence.
• 9 shared timeline inclusion/group configuration tests and all 18 Web codegen/timeline/catalog tests passed.
• Android client and desktop Kotlin compilation passed; the iOS simulator KotlinSharedUI framework linked, and all 21 Apple Core Swift files passed type checking against that framework.
• Weibo module iOS/macOS/Wasm compilation, Web Kotlin library generation, and scoped ktlint checks passed.

Limits:

• Authenticated Weibo account and device UI validation remain pending.
• Full svelte-check still reports 7 existing IconType errors in 4 untouched files; the same diagnostics were reproduced with the pre-change Web sources.