feat: replace Docling with structured local knowledge search

[salim4n]

Summary

• remove Docling from the runtime and replace it with isolated Bun extractors for PDF, DOCX, PPTX and XLSX
• migrate knowledge embeddings to pinned Qwen3 via private TEI gRPC and add versioned ParadeDB hybrid search with BGE reranking
• add durable extraction metadata, provenance, model-revision migrations and deployment sizing documentation

Validation

• bun run check
  • 587 Bun unit/HTTP tests
  • 43 crawler tests
  • TypeScript, architecture, backend and Next.js production build
• bun run test:integration
  • 153 PostgreSQL integration tests
• changed-file secret scan and git diff --check

Safety

• no provider canary or outbound send executed
• no OpenAI embedding fallback retained
• no Docling service or secret remains in the standard runtime