feat(operator): visual-only screens with real-data overview (O.7)

- Overview (pages/index.vue): KPIs from real /tenants /partners /users,
  status meter, recent + needs-follow-up tables. Mock activity stream and
  incident banner overlay come from data/fixtures.ts.
- Operator team: real GET /users filtered to platformAdmin === true,
  with last-seen + tenant counts.
- Users (global): real read with All/Admins/Inactive views and search.
- Infrastructure / Feature flags / Audit: mock fixtures only — wiring to
  real backends (Prometheus, OpenFeature, append-only audit) is tracked
  as follow-ups in OPERATOR-PLAN.md.
- Placeholder pages (support/billing/reports/settings) via OpPlaceholder.
- Shared: Stat, MetricCell, OpPlaceholder components, /api/users proxy,
  PlatformUser type.
- .gitignore: scope the docker volumes data/ rule so apps/*/data/ is
  tracked again (operator carries mock fixtures there).

apps/operator/components/OpPlaceholder.vue

@@ -0,0 +1,64 @@
+<script setup lang="ts">
+import type { IconName } from './UiIcon.vue'
+
+defineProps<{
+  title: string
+  eyebrow?: string
+  icon: IconName
+  body: string
+}>()
+</script>
+
+<template>
+  <div class="placeholder">
+    <PageHeader :eyebrow="eyebrow" :title="title" />
+    <div class="frame">
+      <div class="empty">
+        <div class="icon-tile">
+          <UiIcon :name="icon" :size="22" />
+        </div>
+        <div class="title">{{ title }}</div>
+        <p>{{ body }}</p>
+        <Mono dim>// implementation pending — see OPERATOR-PLAN.md follow-ups</Mono>
+      </div>
+    </div>
+  </div>
+</template>
+
+<style scoped>
+.frame { padding: 32px 40px 64px 40px; }
+.empty {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  gap: 16px;
+  padding: 64px 32px;
+  border: 1px dashed var(--border);
+  border-radius: 12px;
+  background: var(--surface);
+  text-align: center;
+}
+.icon-tile {
+  width: 48px;
+  height: 48px;
+  border-radius: 8px;
+  background: var(--bg);
+  border: 1px solid var(--border);
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  color: var(--text-dim);
+}
+.title {
+  font-family: var(--font-display);
+  font-weight: 600;
+  font-size: 18px;
+}
+p {
+  color: var(--text-dim);
+  font-size: 13px;
+  max-width: 380px;
+  margin: 0;
+}
+</style>