chore(client): 絵文字の画像読み込みに失敗した際はテキストではなくダミー画像を表示

packages/frontend/src/components/global/MkCustomEmoji.stories.impl.ts

@@ -48,3 +48,10 @@ export const Missing = {
 		name: Default.args.name,
 	},
 } satisfies StoryObj<typeof MkCustomEmoji>;
+export const Error = {
+	...Default,
+	args: {
+		url: 'https://example.com/404',
+		name: Default.args.name,
+	},
+} satisfies StoryObj<typeof MkCustomEmoji>;

packages/frontend/src/components/global/MkCustomEmoji.vue

@@ -4,7 +4,12 @@ SPDX-License-Identifier: AGPL-3.0-only
 -->
 
 <template>
-<span v-if="errored">:{{ customEmojiName }}:</span>
+<img
+	v-if="errored"
+	:class="[$style.root, { [$style.normal]: normal, [$style.noStyle]: noStyle }]"
+	src="/client-assets/dummy.png"
+	:title="alt"
+/>
 <img
 	v-else
 	:class="[$style.root, { [$style.normal]: normal, [$style.noStyle]: noStyle }]"