feat(web): custom avatar in create-bot + Settings

Adds AvatarUpload to the create-bot form (PUT on new bot id after POST)
and a CustomAvatarRow per-bot in the profile-toggles section (GET on
mount, PUT/DELETE on user action with initializing guard).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web/src/components/CustomAvatarRow.vue

@@ -0,0 +1,53 @@
+<template>
+  <AvatarUpload v-model="avatarDataUrl" />
+</template>
+
+<script setup lang="ts">
+import { ref, onMounted, watch } from 'vue';
+import axios from 'axios';
+import AvatarUpload from './AvatarUpload.vue';
+
+const props = defineProps<{ botId: string }>();
+const avatarDataUrl = ref<string | null>(null);
+let initializing = true;
+
+async function loadCurrent() {
+  try {
+    const res = await axios.get(`/api/bot/${props.botId}/avatar`, { responseType: 'blob' });
+    const blob = res.data as Blob;
+    avatarDataUrl.value = await blobToDataUrl(blob);
+  } catch (err: any) {
+    if (err?.response?.status !== 404) {
+      console.warn('failed to load avatar', err);
+    }
+    avatarDataUrl.value = null;
+  } finally {
+    initializing = false;
+  }
+}
+
+function blobToDataUrl(blob: Blob): Promise<string> {
+  return new Promise((resolve, reject) => {
+    const reader = new FileReader();
+    reader.onload = () => resolve(reader.result as string);
+    reader.onerror = () => reject(reader.error);
+    reader.readAsDataURL(blob);
+  });
+}
+
+watch(avatarDataUrl, async (newVal, oldVal) => {
+  if (initializing) return;
+  if (newVal === oldVal) return;
+  try {
+    if (newVal && newVal.startsWith('data:')) {
+      await axios.put(`/api/bot/${props.botId}/avatar`, { dataUrl: newVal });
+    } else if (newVal === null) {
+      await axios.delete(`/api/bot/${props.botId}/avatar`);
+    }
+  } catch (err) {
+    console.warn('avatar update failed', err);
+  }
+});
+
+onMounted(loadCurrent);
+</script>