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/Stat.vue

@@ -0,0 +1,45 @@
+<script setup lang="ts">
+withDefaults(
+  defineProps<{
+    label: string
+    value: string | number
+    delta?: string
+    deltaTone?: 'up' | 'down'
+    hint?: string
+  }>(),
+  { deltaTone: 'up' },
+)
+</script>
+
+<template>
+  <div class="stat">
+    <Eyebrow>{{ label }}</Eyebrow>
+    <div class="value">{{ value }}</div>
+    <div v-if="delta || hint" class="meta">
+      <span v-if="delta" class="delta" :data-tone="deltaTone">{{ delta }}</span>
+      <Mono v-if="hint" dim>{{ hint }}</Mono>
+    </div>
+  </div>
+</template>
+
+<style scoped>
+.stat { display: flex; flex-direction: column; gap: 6px; min-width: 0; }
+.value {
+  font-family: var(--font-display);
+  font-weight: 600;
+  font-size: 26px;
+  letter-spacing: -0.02em;
+  line-height: 1;
+  font-variant-numeric: tabular-nums;
+}
+.meta { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
+.delta {
+  font-family: var(--font-mono);
+  font-size: 11px;
+  font-weight: 600;
+  padding: 2px 6px;
+  border-radius: 4px;
+}
+.delta[data-tone='up']   { background: rgba(31, 138, 91, 0.12); color: var(--ok); }
+.delta[data-tone='down'] { background: rgba(226, 48, 48, 0.12); color: var(--bad); }
+</style>