Restructure: Move 43 files into 8 domain packages (backend-lehrer)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend-lehrer/units/analytics_api.py

@@ -0,0 +1,25 @@
+"""
+Breakpilot Drive - Unit Analytics API — Barrel Re-export.
+
+Erweiterte Analytics fuer Lernfortschritt:
+- Pre/Post Gain Visualisierung
+- Misconception-Tracking
+- Stop-Level Analytics
+- Aggregierte Klassen-Statistiken
+- Export-Funktionen
+
+Split into:
+  - unit_analytics_models.py: Pydantic models & enums
+  - unit_analytics_helpers.py: Database access & computation helpers
+  - unit_analytics_routes.py: Core analytics endpoint handlers
+  - unit_analytics_export.py: Export & dashboard endpoints
+"""
+
+from fastapi import APIRouter
+
+from .analytics_routes import router as _routes_router
+from .analytics_export import router as _export_router
+
+router = APIRouter(prefix="/api/analytics", tags=["Unit Analytics"])
+router.include_router(_routes_router)
+router.include_router(_export_router)