- Add expert_cache.py: TTL-based in-memory cache (1 hour default)
- Add expert_source_service.py: WikidataProvider and ConceptNetProvider
- Wikidata SPARQL queries for occupations with Chinese labels
- ConceptNet API queries for occupation-related concepts
- Random selection from cached pool
- Update schemas.py: Add ExpertSource enum (llm/wikidata/conceptnet)
- Update ExpertTransformationRequest with expert_source and expert_language
- Update router: Conditionally use external sources with LLM fallback
- New SSE events: expert_source, expert_fallback
- Update frontend types with ExpertSource
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Co-Authored-By: Claude <noreply@anthropic.com>