feat: Vendor-level consent + Consent analytics (F4 + F6)

F4: Granular Vendor-Level Consent
- Migration 113: vendor_consents JSONB on banner_consents + audit_log
- ConsentCreate schema + BannerConsentDB model extended
- banner_consent_service stores vendor_consents alongside categories
- Audit trail includes vendor-level decisions + user_agent

F6: Consent Rate Analytics
- Migration 114: user_agent on audit_log + time-series index
- BannerAnalyticsService: time series, category breakdown, device stats
- banner_analytics_routes: 4 endpoints (overview, time-series, categories, devices)
- AnalyticsDashboard.tsx: KPIs, bar chart, category bars, device breakdown
- New "Analytik" tab in cookie-banner page

[migration-approved]

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

backend-compliance/compliance/api/banner_analytics_routes.py

@@ -0,0 +1,67 @@
+"""
+FastAPI routes for Banner Consent Analytics.
+
+Endpoints:
+  GET /banner/analytics/{site_id}/overview     — high-level stats
+  GET /banner/analytics/{site_id}/time-series  — opt-in rate over time
+  GET /banner/analytics/{site_id}/categories   — acceptance per category
+  GET /banner/analytics/{site_id}/devices      — mobile/desktop/tablet breakdown
+"""
+
+import logging
+from typing import Optional
+
+from fastapi import APIRouter, Depends, Query
+from sqlalchemy.orm import Session
+
+from classroom_engine.database import get_db
+from .tenant_utils import get_tenant_id as _get_tenant_id
+from compliance.services.banner_analytics_service import BannerAnalyticsService
+
+logger = logging.getLogger(__name__)
+router = APIRouter(prefix="/banner/analytics", tags=["banner-analytics"])
+
+
+@router.get("/{site_id}/overview")
+def analytics_overview(
+    site_id: str,
+    days: int = Query(30, le=365),
+    db: Session = Depends(get_db),
+    tenant_id: str = Depends(_get_tenant_id),
+):
+    service = BannerAnalyticsService(db)
+    return service.get_overview_stats(tenant_id, site_id, days)
+
+
+@router.get("/{site_id}/time-series")
+def analytics_time_series(
+    site_id: str,
+    period: str = Query("daily"),
+    days: int = Query(30, le=365),
+    db: Session = Depends(get_db),
+    tenant_id: str = Depends(_get_tenant_id),
+):
+    service = BannerAnalyticsService(db)
+    return service.get_time_series(tenant_id, site_id, period, days)
+
+
+@router.get("/{site_id}/categories")
+def analytics_categories(
+    site_id: str,
+    days: int = Query(30, le=365),
+    db: Session = Depends(get_db),
+    tenant_id: str = Depends(_get_tenant_id),
+):
+    service = BannerAnalyticsService(db)
+    return service.get_category_breakdown(tenant_id, site_id, days)
+
+
+@router.get("/{site_id}/devices")
+def analytics_devices(
+    site_id: str,
+    days: int = Query(30, le=365),
+    db: Session = Depends(get_db),
+    tenant_id: str = Depends(_get_tenant_id),
+):
+    service = BannerAnalyticsService(db)
+    return service.get_device_breakdown(tenant_id, site_id, days)