fix(campaigns): show the real balance on a prepay ad account

"Balance: INR 0.00" was technically accurate and completely misleading —
that field means amount owed, not money on deposit, and it is 0 by design
on a prepay account right after funds are added. A prepay account now
shows "Available funds" using Meta's own display string instead
(e.g. "Available balance (₹50.00 INR)"); a post-pay account is unaffected
and still shows Balance as before.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/api/types/campaign.ts

@@ -84,6 +84,14 @@ export interface AdAccount {
   min_daily_budget?: number;
   is_prepay_account?: boolean;
   funding_source?: string;
+  /**
+   * On a prepay account, `balance` is the amount owed — 0 even with money
+   * loaded, because nothing has been billed yet. The wallet amount is only
+   * available here, as a string Meta has already formatted for display
+   * (e.g. "Available balance (₹50.00 INR)"); Graph exposes no separate
+   * number for it.
+   */
+  funding_source_details?: { id?: string; display_string?: string; type?: number };
   account_status?: number;
 }
 

src/pages/Campaigns/index.tsx

@@ -134,10 +134,25 @@ export default function CampaignsPage() {
       {account && (
         <Card title="Ad account">
           <Space size="large" wrap>
-            <Statistic
-              title="Balance"
-              value={money(account.balance, account.currency)}
-            />
+            {account.is_prepay_account ? (
+              // On a prepay account "balance" means amount owed, which is
+              // legitimately 0 even with money loaded — nothing has been
+              // billed yet. Meta only exposes the wallet amount as an
+              // already-formatted string, not a separate number, so that
+              // is what gets shown here instead of a confusing "0.00".
+              <Statistic
+                title="Available funds"
+                value={
+                  account.funding_source_details?.display_string ??
+                  "No funding source"
+                }
+              />
+            ) : (
+              <Statistic
+                title="Balance"
+                value={money(account.balance, account.currency)}
+              />
+            )}
             <Statistic
               title="Lifetime spend"
               value={money(account.amount_spent, account.currency)}