feat: Change translation keys to fallback strings

src/lib/components/chat/Messages/Placeholder.svelte

@@ -66,9 +66,9 @@
 					</div>
 				{/if}
 			{:else}
-				<div class=" line-clamp-1">{$i18n.t('Hello', { name: $user.name })}</div>
+				<div class=" line-clamp-1">{$i18n.t('Hello, {{name}}', { name: $user.name })}</div>
 
-				<div>{$i18n.t('GreetingPlaceholder')}</div>
+				<div>{$i18n.t('How can I help you today?')}</div>
 			{/if}
 		</div>
 	</div>