feat(gui-v2): StateBlock 3-state wrapper (exhaustive Vitest, no @visual per constraint #5)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/app/src/components-v2/shared/StateBlock.vue

@@ -0,0 +1,77 @@
+<script setup lang="ts">
+/**
+ * StateBlock — the CLAUDE.md mandatory three-state wrapper (loading /
+ * error / empty) + success passthrough. Built fresh (no crewli-starter
+ * source). Per Plan 3 constraint #5 this component intentionally has
+ * NO @visual baseline yet (self-baseline is tautological); correctness
+ * is locked by the exhaustive Vitest spec. Visual baseline is a
+ * Plans 4–5 follow-up after first real page usage.
+ */
+import Skeleton from 'primevue/skeleton'
+import Message from 'primevue/message'
+import Button from 'primevue/button'
+import Card from 'primevue/card'
+
+defineProps<{
+  state: 'loading' | 'error' | 'empty' | 'success'
+  errorMessage?: string
+  emptyMessage?: string
+  actionLabel?: string
+  retryLabel?: string
+}>()
+
+const emit = defineEmits<{ retry: []; action: [] }>()
+</script>
+
+<template>
+  <div
+    v-if="state === 'loading'"
+    class="flex flex-col gap-3"
+    data-state="loading"
+  >
+    <Skeleton height="2rem" />
+    <Skeleton
+      height="2rem"
+      width="80%"
+    />
+    <Skeleton
+      height="2rem"
+      width="60%"
+    />
+  </div>
+
+  <Message
+    v-else-if="state === 'error'"
+    severity="error"
+    :closable="false"
+    data-state="error"
+  >
+    <div class="flex items-center justify-between gap-4 w-full">
+      <span>{{ errorMessage ?? 'Er ging iets mis.' }}</span>
+      <Button
+        :label="retryLabel ?? 'Opnieuw proberen'"
+        size="small"
+        @click="emit('retry')"
+      />
+    </div>
+  </Message>
+
+  <Card
+    v-else-if="state === 'empty'"
+    data-state="empty"
+    :pt="{ root: 'border border-dashed border-[var(--p-content-border-color)] shadow-none', content: 'flex flex-col items-center gap-3 py-10 text-center' }"
+  >
+    <template #content>
+      <p class="m-0 text-[var(--p-text-muted-color)]">
+        {{ emptyMessage ?? 'Nog niets om te tonen.' }}
+      </p>
+      <Button
+        v-if="actionLabel"
+        :label="actionLabel"
+        @click="emit('action')"
+      />
+    </template>
+  </Card>
+
+  <slot v-else />
+</template>