fix: remove /api/ double-prefix from all frontend API calls

Frontend api.ts baseUrl is already "/api", so paths like
"/api/cases" produced "/api/api/cases". Stripped the redundant
prefix from all component calls. Rewrite destination correctly
adds /api/ back for the Go backend.

frontend/src/components/settings/CalDAVSettings.tsx

@@ -57,7 +57,7 @@ export function CalDAVSettings({ tenant }: { tenant: Tenant }) {
   // Fetch sync status
   const { data: syncStatus } = useQuery({
     queryKey: ["caldav-status"],
-    queryFn: () => api.get<CalDAVSyncResponse>("/api/caldav/status"),
+    queryFn: () => api.get<CalDAVSyncResponse>("/caldav/status"),
     refetchInterval: 30_000,
   });
 
@@ -83,7 +83,7 @@ export function CalDAVSettings({ tenant }: { tenant: Tenant }) {
 
   // Trigger sync
   const syncMutation = useMutation({
-    mutationFn: () => api.post<CalDAVSyncResponse>("/api/caldav/sync"),
+    mutationFn: () => api.post<CalDAVSyncResponse>("/caldav/sync"),
     onSuccess: (result) => {
       queryClient.invalidateQueries({ queryKey: ["caldav-status"] });
       if (result.status === "ok") {