feat(customers): opt-in debug block on the omde lists, printed in the panel console

Sending X-Debug: 1 makes the five wholesale list endpoints return a counts-only
`debug` block next to the rows: the WHERE that actually ran, how many customers
the scope matches before the grid's own filters, how many customers exist per
kind/active/archived/step and how many are an expert's trading account. The
panel sends the header and console-logs the block when localStorage.debug === '1'.

Off by default; DIAG_LOG=false disables it server-side. No names or mobiles.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

apps/api/src/modules/admin-customers/admin-customers.service.ts

@@ -296,7 +296,39 @@ export class AdminCustomersService {
     }
   }
 
-  async list(query: TableQueryDto, scope: OmdeScope = 'all') {
+  /**
+   * Opt-in (X-Debug header) troubleshooting block for an empty list: counts only,
+   * no names/mobiles. Shows the exact WHERE the request ran, how many customers
+   * the scope matches before the grid's own filters, and how many customers
+   * exist per kind / are an expert's trading account. Off with DIAG_LOG=false.
+   */
+  private async listDebug(
+    scope: OmdeScope,
+    scoped: Prisma.CustomerWhereInput,
+    total: number,
+    returned: number,
+  ) {
+    const [byKind, inScope, expertTradingAccounts] = await Promise.all([
+      this.prisma.customer.groupBy({
+        by: ['kind', 'isActive', 'isArchived', 'verificationStep'],
+        _count: { _all: true },
+      }),
+      this.prisma.customer.count({ where: this.scopeWhere(scope) }),
+      this.prisma.customer.count({ where: { salesExpertTradingFor: { isNot: null } } }),
+    ]);
+    return {
+      scope,
+      where: scoped,
+      matched_with_grid_filters: total,
+      returned_rows: returned,
+      matched_by_scope_only: inScope,
+      customers_total: byKind.reduce((n, g) => n + g._count._all, 0),
+      expert_trading_accounts: expertTradingAccounts,
+      by_kind: byKind.map(({ _count, ...g }) => ({ ...g, n: _count._all })),
+    };
+  }
+
+  async list(query: TableQueryDto, scope: OmdeScope = 'all', debug = false) {
     this.table.assertNotExport(query);
     const aliased = this.applyAliases(query);
 
@@ -325,13 +357,15 @@ export class AdminCustomersService {
     ]);
 
     const linked = await this.accountingLinked(rows.map((r) => r.id));
-    return this.table.respond(
+    const result = this.table.respond(
       rows.map((r) => ({ ...this.toRow(r), ...AdminCustomersService.accountingCells(r, linked) })),
       total,
       query,
       page,
       limit,
     );
+    if (!debug || process.env.DIAG_LOG === 'false') return result;
+    return { ...result, debug: await this.listDebug(scope, scoped, total, rows.length) };
   }
 
   /**