refactor: update application code to use unified configuration

- Update App.tsx to use getAppConfig() instead of import.meta.env
- Update email templates to use getAppConfig() for base URL
- Update database strategy to use getDatabaseConfig() function
- Update mailgun service to use getter functions
- Remove direct unified config imports in favor of functions
- Ensure consistent configuration access throughout codebase

App.tsx

@@ -6,6 +6,7 @@ import React, {
   useRef,
 } from 'react';
 import { generateSchedule, generateReminderSchedule } from './utils/schedule';
+import { getAppConfig } from './utils/env';
 import {
   Medication,
   Dose,
@@ -115,7 +116,7 @@ const Header: React.FC<{
           className='hidden sm:flex items-center space-x-2 px-4 py-2 text-sm font-medium text-slate-700 bg-slate-100 rounded-lg hover:bg-slate-200 transition-colors dark:bg-slate-700 dark:text-slate-200 dark:hover:bg-slate-600'
         >
           <MenuIcon className='w-4 h-4' aria-hidden='true' />
-          <span>{import.meta.env.VITE_APP_NAME || 'Meds'}</span>
+          <span>{getAppConfig().name}</span>
         </button>
         <button
           onClick={onManageReminders}