Add tool to update account balance to MCP server

apps/api/src/app/endpoints/mcp/mcp.schemas.spec.ts

@@ -336,6 +336,11 @@ describe('UPDATE_ACCOUNT_BALANCE_PARAMETERS', () => {
     expect(parse({ date: '2026-09-03' })).toBe(true);
   });
 
+  // A user in a time zone east of UTC has already reached the next date
+  it('Accepts a cash balance of tomorrow in UTC', () => {
+    expect(parse({ date: '2026-09-04' })).toBe(true);
+  });
+
   it('Accepts a negative cash balance', () => {
     expect(parse({ balance: -1000 })).toBe(true);
   });

apps/api/src/app/endpoints/mcp/mcp.service.spec.ts

@@ -668,6 +668,10 @@ describe('McpService', () => {
         HttpException
       );
 
+      // The permission is checked first, hence the existence of the account
+      // stays hidden
+      expect(accountService.account).not.toHaveBeenCalled();
+
       expect(
         accountBalanceService.createOrUpdateAccountBalance
       ).not.toHaveBeenCalled();