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/MetricCell.vue

@@ -0,0 +1,32 @@
+<script setup lang="ts">
+defineProps<{ label: string; value: string; tone?: 'ok' | 'warn' | 'bad' }>()
+</script>
+
+<template>
+  <div class="cell">
+    <div class="label">{{ label }}</div>
+    <div class="value" :data-tone="tone">{{ value }}</div>
+  </div>
+</template>
+
+<style scoped>
+.cell { min-width: 0; }
+.label {
+  font-family: var(--font-mono);
+  font-size: 9px;
+  letter-spacing: 0.12em;
+  text-transform: uppercase;
+  color: var(--text-mute);
+}
+.value {
+  font-family: var(--font-mono);
+  font-size: 14px;
+  font-weight: 600;
+  margin-top: 4px;
+  font-variant-numeric: tabular-nums;
+  color: var(--text);
+}
+.value[data-tone='ok']   { color: var(--ok); }
+.value[data-tone='warn'] { color: var(--warn); }
+.value[data-tone='bad']  { color: var(--bad); }
+</style>