fix(sdk)+docs: dsfa-visibleWhen Bug, training.md, index.md komplett

Fixes:
- types.ts: dsfa isOptional false→true + visibleWhen ergänzt
  (sichtbar nur bei Scope L2/L3/L4 oder dsfaRequired Hard-Trigger)
- dsfa war einziger Step mit fehlendem visibleWhen laut Plan

Docs:
- training.md: NEU — Training Engine (seq 4800), alle Endpoints,
  Rollenmatrix, KI-Inhalt, Quiz, TTS-Media, DB-Schema
- mkdocs.yml: Training Engine nav-Eintrag
- index.md: E-Mail-Templates (4350) + Training Engine (4800)
  in Modul-Tabelle + URL-Liste ergänzt

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

admin-compliance/lib/sdk/types.ts

@@ -618,7 +618,13 @@ export const SDK_STEPS: SDKStep[] = [
     url: '/sdk/dsfa',
     checkpointId: 'CP-DSFA',
     prerequisiteSteps: ['obligations'],
-    isOptional: false,
+    isOptional: true,
+    visibleWhen: (state) => {
+      const level = state.complianceScope?.decision?.determinedLevel
+      if (level && ['L2', 'L3', 'L4'].includes(level)) return true
+      const triggers = state.complianceScope?.decision?.triggeredHardTriggers || []
+      return triggers.some(t => t.rule.dsfaRequired)
+    },
   },
   {
     id: 'tom',