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/components/dashboard/UpcomingTimeline.tsx

@@ -1,8 +1,9 @@
 "use client";
 
+import Link from "next/link";
 import { format, parseISO, isToday, isTomorrow } from "date-fns";
 import { de } from "date-fns/locale";
-import { Clock, Calendar, MapPin } from "lucide-react";
+import { Clock, Calendar, MapPin, ChevronRight } from "lucide-react";
 import type { UpcomingDeadline, UpcomingAppointment } from "@/lib/types";
 
 interface Props {
@@ -80,8 +81,12 @@ export function UpcomingTimeline({ deadlines, appointments }: Props) {
 function TimelineEntry({ item }: { item: TimelineItem }) {
   if (item.type === "deadline") {
     const d = item.data;
+    const href = `/fristen/${d.id}`;
     return (
-      <div className="flex items-start gap-3 rounded-lg border border-neutral-100 bg-neutral-50/50 px-3 py-2.5">
+      <Link
+        href={href}
+        className="group flex items-start gap-3 rounded-lg border border-neutral-100 bg-neutral-50/50 px-3 py-2.5 transition-colors hover:border-neutral-200 hover:bg-neutral-100/50"
+      >
         <div className="mt-0.5 rounded-md bg-amber-50 p-1">
           <Clock className="h-3.5 w-3.5 text-amber-500" />
         </div>
@@ -90,19 +95,40 @@ function TimelineEntry({ item }: { item: TimelineItem }) {
             {d.title}
           </p>
           <p className="mt-0.5 truncate text-xs text-neutral-500">
-            {d.case_number} · {d.case_title}
+            {d.case_id ? (
+              <span
+                onClick={(e) => e.stopPropagation()}
+                className="inline"
+              >
+                <Link
+                  href={`/cases/${d.case_id}`}
+                  className="underline decoration-neutral-300 hover:text-neutral-900 hover:decoration-neutral-500"
+                >
+                  {d.case_number}
+                </Link>
+                {" · "}
+              </span>
+            ) : (
+              <>{d.case_number} · </>
+            )}
+            {d.case_title}
           </p>
         </div>
-        <span className="shrink-0 text-xs font-medium text-amber-600">
-          Frist
-        </span>
-      </div>
+        <div className="flex shrink-0 items-center gap-1.5">
+          <span className="text-xs font-medium text-amber-600">Frist</span>
+          <ChevronRight className="h-3.5 w-3.5 text-neutral-300 transition-colors group-hover:text-neutral-500" />
+        </div>
+      </Link>
     );
   }
 
   const a = item.data;
+  const href = `/termine/${a.id}`;
   return (
-    <div className="flex items-start gap-3 rounded-lg border border-neutral-100 bg-neutral-50/50 px-3 py-2.5">
+    <Link
+      href={href}
+      className="group flex items-start gap-3 rounded-lg border border-neutral-100 bg-neutral-50/50 px-3 py-2.5 transition-colors hover:border-neutral-200 hover:bg-neutral-100/50"
+    >
       <div className="mt-0.5 rounded-md bg-blue-50 p-1">
         <Calendar className="h-3.5 w-3.5 text-blue-500" />
       </div>
@@ -121,7 +147,20 @@ function TimelineEntry({ item }: { item: TimelineItem }) {
               </span>
             </>
           )}
-          {a.case_number && (
+          {a.case_number && a.case_id && (
+            <>
+              <span className="text-neutral-300">·</span>
+              <span onClick={(e) => e.stopPropagation()}>
+                <Link
+                  href={`/cases/${a.case_id}`}
+                  className="underline decoration-neutral-300 hover:text-neutral-900 hover:decoration-neutral-500"
+                >
+                  {a.case_number}
+                </Link>
+              </span>
+            </>
+          )}
+          {a.case_number && !a.case_id && (
             <>
               <span className="text-neutral-300">·</span>
               <span>{a.case_number}</span>
@@ -129,9 +168,10 @@ function TimelineEntry({ item }: { item: TimelineItem }) {
           )}
         </div>
       </div>
-      <span className="shrink-0 text-xs font-medium text-blue-600">
-        Termin
-      </span>
-    </div>
+      <div className="flex shrink-0 items-center gap-1.5">
+        <span className="text-xs font-medium text-blue-600">Termin</span>
+        <ChevronRight className="h-3.5 w-3.5 text-neutral-300 transition-colors group-hover:text-neutral-500" />
+      </div>
+    </Link>
   );
 }