feat: add message editing

This commit adds message editing as a feature. To accomplish this, the settings
dialog was refactored into a singleton and now the message edit and settings
use the singleton where appropriate.

app/components/Dialog/Textbox.vue

@@ -0,0 +1,24 @@
+<script setup lang="ts">
+const props = defineProps<{
+    title?: string;
+    initialValue?: string;
+}>();
+
+const emit = defineEmits(['confirm', 'cancel']);
+const text = ref(props.initialValue || '');
+</script>
+
+<template>
+    <div class="flex flex-col w-full">
+        <h3 class="m-4" v-if="title">{{ title }}</h3>
+        <textarea v-model="text" class="bg-[var(--bg-surface)] resize-none h-full w-full p-2 rounded" />
+        <div class="flex justify-end gap-2 m-2">
+            <button
+                class="px-2 py-1 rounded-lg border border-[var(--color-border)] hover:bg-[var(--color-hover)] transition-[background-color] duration-200"
+                @click="emit('cancel')">Cancel</button>
+            <button
+                class="px-2 py-1 rounded-lg bg-[var(--color-accent)] text-[var(--color-accent-text)] hover:bg-[var(--color-accent-hover)] transition-[background-color] duration-200"
+                @click="emit('confirm', text)">Confirm</button>
+        </div>
+    </div>
+</template>