feat: Add APP_NAME env support for branding and deployment

- Make app name configurable via APP_NAME env variable - Update UI,
HTML, Docker, scripts, and k8s to use APP_NAME - Add process-html.sh for
template substitution - Document APP_NAME usage in
docs/APP_NAME_CONFIGURATION.md - Update Dockerfile, compose, and scripts
for dynamic naming - Add index.html.template for environment-based
branding

App.tsx

@@ -116,7 +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>Meds</span>
+          <span>{import.meta.env.VITE_APP_NAME || 'Meds'}</span>
         </button>
         <button
           onClick={onManageReminders}