feat(iace): open-source safety KB sources + bp_iace_safety_kb (Thema 2)

Versioned, license-tagged source docs for the multi-layer GT knowledge base,
ingested into the new core RAG collection bp_iace_safety_kb (whitelisted in
the RAG search handler):
- prism_risk_methodology.md — OPSS PRISM v2 (OGL v3): full severity(4)×
  probability(8) → risk-level matrix (Serious/High/Medium/Low), RAPEX-aligned.
- cobot_biomech_limits.md — CC BY 4.0 papers (Behrens 2022 / Park 2019):
  force (N) & pressure (N/cm²) pain thresholds by body region (the data behind
  ISO/TS 15066, cited from the open papers — standard tables NOT reproduced).
- hse_example_risk_assessments.md — HSE (OGL v3): qualitative hazard→control.
- osha_robot_safety.md — OSHA OTM (public domain): 250 mm/s teach anchor,
  robot hazard taxonomy, safeguarding hierarchy.

No DIN/EN/ISO/IEC/DGUV content reproduced; each doc states its license + attribution.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

ai-compliance-sdk/internal/api/handlers/rag_handlers.go

@@ -34,6 +34,7 @@ var AllowedCollections = map[string]bool{
 	"bp_legal_templates":        true,
 	"bp_iace_libraries":         true,
 	"bp_iace_accident_stats":    true,
+	"bp_iace_safety_kb":         true,
 }
 
 // SearchRequest represents a RAG search request.