feat(saas): add knowledge base module — categories, items, versions, search, analytics
- 5 knowledge tables (categories, items, chunks, versions, usage) with pgvector + HNSW + GIN indexes
- 23+ API routes covering full CRUD, tree-structured categories, version snapshots
- Keyword-based search with ILIKE + array match (placeholder for vector search)
- Analytics endpoints: overview, trends, top-items, quality, gaps
- Markdown-aware content chunking with overlap strategy
- Worker dispatch for async embedding generation
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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