chore(admin): rename pending_payment label and tier→contribution

Backlog cleanup from docs/LAUNCH_READINESS.md:
- B4: admin status filter + form options + STATUS_LABELS now read
  "Payment setup incomplete" so admins stop conflating with membership state
- CSV import preview header "Tier" → "Contribution"
- handleUpdateTier → handleUpdateContribution on /member/account
- update-contribution error log "tier" → "amount"

app/pages/admin/members/index.vue

@@ -42,7 +42,7 @@
         <select v-model="statusFilter" aria-label="Filter by status">
           <option value="">All Statuses</option>
           <option value="active">Active</option>
-          <option value="pending_payment">Pending Payment</option>
+          <option value="pending_payment">Payment setup incomplete</option>
           <option value="suspended">Suspended</option>
           <option value="cancelled">Cancelled</option>
         </select>
@@ -269,7 +269,7 @@
                     <th>Name</th>
                     <th>Email</th>
                     <th>Circle</th>
-                    <th>Tier</th>
+                    <th>Contribution</th>
                   </tr>
                 </thead>
                 <tbody>
@@ -373,7 +373,7 @@
           <div class="field">
             <label>Status</label>
             <select v-model="editingMember.status">
-              <option value="pending_payment">Pending Payment</option>
+              <option value="pending_payment">Payment setup incomplete</option>
               <option value="active">Active</option>
               <option value="suspended">Suspended</option>
               <option value="cancelled">Cancelled</option>
@@ -490,7 +490,7 @@ const sortDir = ref("desc");
 
 const STATUS_LABELS = {
   active: "Active",
-  pending_payment: "Pending",
+  pending_payment: "Payment setup incomplete",
   suspended: "Suspended",
   cancelled: "Cancelled",
 };