feat: Phase B — interactive dashboard, breadcrumbs, clickable navigation

- Breadcrumb component: reusable nav with items array (label+href)
- DeadlineTrafficLights: buttons → Links to /fristen?status={filter}
- CaseOverviewGrid: static metrics → clickable Links to /cases?status={filter}
- UpcomingTimeline: items → clickable Links to /fristen/{id} or /termine/{id}
  with case number links and hover chevron
- QuickActions: swap CalDAV Sync for "Neuer Termin" → /termine/neu,
  fix "Frist eintragen" → /fristen/neu
- AISummaryCard: add RefreshCw button with spinning animation
- RecentActivityList: new component showing recent case events
- DeadlineList: accept initialStatus prop, add this_week/ok filters
- fristen/page.tsx: read searchParams.status for initial filter
- Add breadcrumbs to dashboard, fristen, cases, termine pages
- Add RecentActivity type, update DashboardData type

frontend/src/app/(app)/dashboard/page.tsx

@@ -8,6 +8,8 @@ import { CaseOverviewGrid } from "@/components/dashboard/CaseOverviewGrid";
 import { UpcomingTimeline } from "@/components/dashboard/UpcomingTimeline";
 import { AISummaryCard } from "@/components/dashboard/AISummaryCard";
 import { QuickActions } from "@/components/dashboard/QuickActions";
+import { RecentActivityList } from "@/components/dashboard/RecentActivityList";
+import { Breadcrumb } from "@/components/layout/Breadcrumb";
 import { Skeleton, SkeletonCard } from "@/components/ui/Skeleton";
 import { AlertTriangle, RefreshCw } from "lucide-react";
 
@@ -71,9 +73,12 @@ export default function DashboardPage() {
     );
   }
 
+  const recentActivity = Array.isArray(data.recent_activity) ? data.recent_activity : [];
+
   return (
     <div className="animate-fade-in mx-auto max-w-6xl space-y-6">
       <div>
+        <Breadcrumb items={[{ label: "Dashboard" }]} />
         <h1 className="text-lg font-semibold text-neutral-900">Dashboard</h1>
         <p className="mt-0.5 text-sm text-neutral-500">
           Fristenübersicht und Kanzlei-Status
@@ -91,10 +96,14 @@ export default function DashboardPage() {
         </div>
         <div className="space-y-6">
           <CaseOverviewGrid data={data.case_summary ?? { active_count: 0, new_this_month: 0, closed_count: 0 }} />
-          <AISummaryCard data={data} />
+          <AISummaryCard data={data} onRefresh={() => refetch()} />
           <QuickActions />
         </div>
       </div>
+
+      {recentActivity.length > 0 && (
+        <RecentActivityList activities={recentActivity} />
+      )}
     </div>
   );
 }