feat(iace): project-wide risk matrix (Severity × Probability)

Adds GET /projects/:id/risk-matrix — a confidence-aware risk view computed
on read from each hazard's category/scenario/lifecycle using the SAME model
as the GT benchmark (no persistence, so it never goes stale against the
model; the hand-defaulted iace_hazards risk columns stay untouched).

- risk_matrix.go: EstimateHazardRisk (single source of truth for S/F/W/P +
  range + level + confidence) and BuildRiskMatrix (per-hazard list + a 5×5
  Severity×Probability aggregation grid with dominant level per cell).
- Frontend: RiskMatrix grid in the Risikobewertung tab (muted colours per
  the confidence-aware tonality), level counts + tool-confidence summary,
  fed by useRiskMatrix. Shows risk for EVERY project, not only GT ones.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

admin-compliance/app/sdk/iace/[projectId]/risikobewertung/_hooks/useRiskMatrix.ts

@@ -0,0 +1,64 @@
+'use client'
+
+import { useEffect, useState } from 'react'
+
+export interface HazardRiskDetail {
+  hazard_id: string
+  name: string
+  category: string
+  zone: string
+  severity: number
+  frequency: number
+  probability: number
+  avoidance: number
+  risk_point: number
+  risk_low: number
+  risk_high: number
+  level: string
+  level_range: string
+  confidence: string
+}
+
+export interface RiskMatrixCell {
+  severity: number
+  probability: number
+  count: number
+  dominant_level: string
+  hazard_ids: string[]
+}
+
+export interface RiskMatrixData {
+  hazards: HazardRiskDetail[]
+  matrix: RiskMatrixCell[]
+  level_counts: Record<string, number>
+  total: number
+  high_confidence_pct: number
+}
+
+/** Loads the project-wide confidence-aware risk matrix (computed server-side). */
+export function useRiskMatrix(projectId: string) {
+  const [data, setData] = useState<RiskMatrixData | null>(null)
+  const [loading, setLoading] = useState(true)
+
+  useEffect(() => {
+    let cancelled = false
+    async function load() {
+      setLoading(true)
+      try {
+        const res = await fetch(`/api/sdk/v1/iace/projects/${projectId}/risk-matrix`)
+        const json = res.ok ? ((await res.json()) as RiskMatrixData) : null
+        if (!cancelled) setData(json)
+      } catch (err) {
+        console.error('Failed to load risk matrix:', err)
+      } finally {
+        if (!cancelled) setLoading(false)
+      }
+    }
+    load()
+    return () => {
+      cancelled = true
+    }
+  }, [projectId])
+
+  return { data, loading }
+}