m4: per-view error states (board / search / graph / reminders)

Each data view now catches a failed load and shows an explicit error message
with a Retry button, instead of falling through to a misleading empty state.
Pairs with the global error toast: the toast says something failed, the view
says which and offers a retry.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FRgehjoz7Yv8LkUfADxACm

frontend/src/views/BoardView.vue

@@ -14,6 +14,7 @@ const router = useRouter();
 
 const editing = ref<Note | null>(null);
 const quickAdd = ref<InstanceType<typeof QuickAdd> | null>(null);
+const loadError = ref("");
 
 // The global `c` shortcut bumps composeTick; reopen the composer when we're
 // already on the board (a fresh navigation autofocuses it via the prop).
@@ -118,7 +119,12 @@ const emptyState = computed(() => {
 });
 
 async function reload() {
-  await notes.load(currentView.value, currentLabel.value);
+  loadError.value = "";
+  try {
+    await notes.load(currentView.value, currentLabel.value);
+  } catch (e) {
+    loadError.value = (e as { error?: string }).error ?? "Couldn't load your notes.";
+  }
 }
 
 onMounted(() => {
@@ -169,6 +175,18 @@ async function onDrop(target: Note) {
 
     <div v-if="notes.loading" class="py-24 text-center text-sm text-neutral-400">Loading…</div>
 
+    <div v-else-if="loadError" class="py-24 text-center">
+      <h2 class="text-lg font-semibold text-neutral-700 dark:text-neutral-200">Couldn't load your notes</h2>
+      <p class="mt-1 text-sm text-neutral-400">{{ loadError }}</p>
+      <button
+        type="button"
+        class="mt-3 rounded-md border border-neutral-300 px-3 py-1.5 text-sm hover:bg-neutral-100 focus:outline-none focus-visible:ring-2 focus-visible:ring-brand dark:border-neutral-700 dark:hover:bg-neutral-800"
+        @click="reload"
+      >
+        Retry
+      </button>
+    </div>
+
     <div v-else-if="notes.items.length === 0" class="py-24 text-center">
       <h2 class="text-lg font-semibold text-neutral-700 dark:text-neutral-200">{{ emptyState.title }}</h2>
       <p class="mt-1 text-sm text-neutral-400">{{ emptyState.subtitle }}</p>