fix(frontend): replay row-flash on every refetch via dataUpdatedAt key

The previous static key={c.id} let React reuse the same <TableRow>
element across refetches, so animate-row-flash only played on
initial mount and on the first render of a brand-new claim_id.
Updated rows whose claim_id was unchanged never re-flashed.

Re-keying on `${c.id}-${dataUpdatedAt}` re-mounts the row on
every refetch (initial load, filter change, parse invalidation),
so the 1.2s accent-tint flash replays each time.

Also: README's 'Frontend unit tests (when added)' is stale — npm
test now exists and runs 3 passing tests.

hooks: add dataUpdatedAt: 0 to the !isConfigured fallback return
so the pages type-check.

src/pages/Claims.tsx

@@ -63,7 +63,7 @@ export function Claims() {
     offset: (page - 1) * PAGE_SIZE,
   };
 
-  const { data, isLoading, isError, error, refetch } = useClaims(params);
+  const { data, isLoading, isError, error, refetch, dataUpdatedAt } = useClaims(params);
   const items = data?.items ?? [];
 
   const totals = useMemo(
@@ -224,12 +224,12 @@ export function Claims() {
                   const provider = providerMap[c.providerNpi];
                   return (
                     <TableRow
-                      key={c.id}
+                      key={`${c.id}-${dataUpdatedAt}`}
                       className={cn(
                         "animate-row-flash",
-                        // Suppress flash when filtering so only the new
-                        // page's first paint flashes; subsequent renders
-                        // use the existing fade-in from the page wrapper.
+                        // Re-keying on dataUpdatedAt re-mounts the row on
+                        // every refetch (initial load, filter change, parse
+                        // invalidation) so the row-flash keyframe replays.
                       )}
                     >
                       <TableCell>