feat(billing): sync catalog price edits to Stripe + re-price live customers

Editing a catalog amount now propagates beyond MongoDB. Stripe Prices are
immutable, so each changed currency mints a fresh Stripe Price at the new
amount, overwrites the cached stripePriceIds[currency] (which also fixes the
stale-price bug for new subscriptions), and repoints every live subscription
on that (row, currency) onto it with proration_behavior 'none' — the new
amount takes effect at the customer's next billing cycle, no mid-cycle charge.
The per-seat snapshot is refreshed so MRR reflects the go-forward rate.

Before committing the edit, the operator sees a warning with the affected
customer count, driven by a new GET /prices/:id/impact endpoint. Per-sub
failures are logged, never fatal; Stripe-disabled rows still re-snapshot.

apps/operator/pages/pricing.vue

@@ -68,6 +68,17 @@ function cancelEdit(id: string) {
   delete drafts[id]
 }
 
+// A pending price change held back for operator confirmation, because it
+// re-prices live customers. Resolved by confirmReprice() or dismissed.
+interface PendingChange {
+  row: PriceRow
+  next: Partial<Record<Currency, number>>
+  changes: { currency: Currency; from?: number; to: number; affected: number }[]
+  totalAffected: number
+}
+const pending = ref<PendingChange | null>(null)
+const confirmBusy = ref(false)
+
 async function saveEdit(row: PriceRow) {
   const draft = drafts[row._id]
   if (!draft) return
@@ -81,6 +92,45 @@ async function saveEdit(row: PriceRow) {
     }
     next[c] = parsed
   }
+
+  // Which currencies actually changed value? Only those re-price customers.
+  const changedCurrencies = CURRENCIES.filter((c) => next[c] !== undefined && next[c] !== row.amounts[c])
+  if (changedCurrencies.length === 0) {
+    cancelEdit(row._id)  // nothing changed — just close the editor
+    return
+  }
+
+  // Ask the backend how many live customers each changed currency touches.
+  saving.value = row._id
+  let impact: Record<Currency, number> = { DKK: 0, EUR: 0, USD: 0 }
+  try {
+    impact = await $fetch<Record<Currency, number>>(`/api/prices/${row._id}/impact`)
+  } catch {
+    // Impact lookup failed — fall through with zeros; the save still works,
+    // we just can't show the affected-customer count.
+  } finally {
+    saving.value = null
+  }
+
+  const changes = changedCurrencies.map((c) => ({
+    currency: c,
+    from: row.amounts[c],
+    to: next[c]!,
+    affected: impact[c] ?? 0,
+  }))
+  const totalAffected = changes.reduce((sum, ch) => sum + ch.affected, 0)
+
+  // No live customers on the changed currencies → commit straight away.
+  if (totalAffected === 0) {
+    await commitSave(row, next)
+    return
+  }
+  pending.value = { row, next, changes, totalAffected }
+}
+
+// The actual PATCH. Backend mints new Stripe Prices for changed currencies and
+// moves live subs onto them (effective next cycle).
+async function commitSave(row: PriceRow, next: Partial<Record<Currency, number>>) {
   saving.value = row._id
   try {
     await $fetch(`/api/prices/${row._id}`, { method: 'PATCH', body: { amounts: next } })
@@ -95,6 +145,18 @@ async function saveEdit(row: PriceRow) {
   }
 }
 
+async function confirmReprice() {
+  if (!pending.value) return
+  const { row, next } = pending.value
+  confirmBusy.value = true
+  try {
+    await commitSave(row, next)
+  } finally {
+    confirmBusy.value = false
+    pending.value = null
+  }
+}
+
 async function toggleActive(row: PriceRow) {
   saving.value = row._id
   try {
@@ -173,7 +235,7 @@ const sortedPrices = computed<PriceRow[]>(() =>
     <PageHeader
       eyebrow="Operator · operator.dezky.local"
       title="Pricing catalog"
-      subtitle="One row per plan + cycle, with independent prices per currency. Changes affect subscriptions provisioned from now on — existing customers keep the price snapshot taken at provisioning."
+      subtitle="One row per plan + cycle, with independent prices per currency. Editing an amount re-prices live customers on that currency at their next billing cycle (no mid-cycle charge) and applies to all new subscriptions."
     >
       <template #actions>
         <label class="toggle">
@@ -292,6 +354,37 @@ const sortedPrices = computed<PriceRow[]>(() =>
       </div>
     </Card>
     </div>
+
+    <ConfirmDialog
+      :open="pending !== null"
+      eyebrow="Pricing catalog"
+      :title="pending ? `Change ${PLAN_LABEL[pending.row.plan]} · ${CYCLE_LABEL[pending.row.cycle]} pricing?` : ''"
+      confirm-label="Apply change"
+      :busy="confirmBusy"
+      @close="pending = null"
+      @confirm="confirmReprice"
+    >
+      <template v-if="pending">
+        <p>
+          <strong>{{ pending.totalAffected }}</strong>
+          active {{ pending.totalAffected === 1 ? 'customer' : 'customers' }} will move to the
+          new price at their <strong>next billing cycle</strong>. The current period and past
+          invoices are unaffected — no mid-cycle charge or credit.
+        </p>
+        <ul class="reprice-list">
+          <li v-for="ch in pending.changes" :key="ch.currency">
+            <Mono>{{ ch.currency }}</Mono>
+            <span class="reprice-amounts">
+              {{ ch.from !== undefined ? toMajor(ch.from) : '—' }} →
+              <strong>{{ toMajor(ch.to) }}</strong>
+            </span>
+            <span class="reprice-count">
+              {{ ch.affected }} {{ ch.affected === 1 ? 'customer' : 'customers' }}
+            </span>
+          </li>
+        </ul>
+      </template>
+    </ConfirmDialog>
   </div>
 </template>
 
@@ -345,4 +438,18 @@ tr.inactive { opacity: 0.55; }
   outline: 0;
 }
 .hint { font-size: 13px; color: var(--text-dim); margin: 0 0 12px; }
+
+.reprice-list { list-style: none; margin: 14px 0 0; padding: 0; display: flex; flex-direction: column; gap: 8px; }
+.reprice-list li {
+  display: flex;
+  align-items: center;
+  gap: 12px;
+  padding: 10px 12px;
+  background: var(--surface);
+  border: 1px solid var(--border);
+  border-radius: 6px;
+  font-size: 13px;
+}
+.reprice-amounts { font-family: var(--font-mono); font-variant-numeric: tabular-nums; }
+.reprice-count { margin-left: auto; color: var(--text-mute); font-size: 12px; }
 </style>

apps/operator/server/api/prices/[id]/impact.get.ts

@@ -0,0 +1,6 @@
+import { platformApi } from '~~/server/utils/platform-api'
+
+export default defineEventHandler(async (event) => {
+  const id = getRouterParam(event, 'id')
+  return platformApi(event, `/prices/${id}/impact`)
+})