Remove archived thread filters

[ymichael]

Summary

• remove the All / Root / Children filter controls from the archived threads page
• simplify the archived threads query and cache key so it only lists archived threads for the project
• update realtime cache tests for the simplified archived-list key

Validation

• pnpm exec turbo run typecheck --filter=@bb/app
• pnpm exec turbo run test --filter=@bb/app -- src/hooks/realtime-cache-effects.test.ts
• git diff --check