feat(login): list all three registered tenants in the login screen selector

The tenant selector (mifosx-tenant-selector, already wired into the login
page) hides itself whenever fineractPlatformTenantIds resolves to a single
entry -- and env.js only ever listed 'abc_bank', so the dropdown never had
a reason to show even though Socity_bank and, as of this session, Default
Bank are all live, reachable tenants.

Lists all three identifiers exactly as registered in the tenants table
(default, abc_bank, socity_bank) so a user can actually pick which bank to
log into instead of being stuck on whichever one was hardcoded.

src/assets/env.js

@@ -18,7 +18,7 @@
   window["env"]["apiActuator"] = '';
 
   window["env"]["fineractPlatformTenantId"] = 'abc_bank';
-  window["env"]["fineractPlatformTenantIds"] = 'abc_bank';
+  window["env"]["fineractPlatformTenantIds"] = 'default,abc_bank,socity_bank';
 
   window['env']['tenantLogoUrl'] = '';
   window['env']['tenantLogoUrlDark'] = '';