refactor(web): refactor avatar assets to use PNG instead of inline SVG

- TravelReimbursementCreateView.js: change avatar imports to use PNG paths
- web/public/assets: add PNG avatar assets (header.png, person.png)

web/src/views/scripts/TravelReimbursementCreateView.js

@@ -1,11 +1,12 @@
 import { computed, nextTick, onBeforeUnmount, onMounted, ref } from 'vue'
 
-import aiAvatar from '../../assets/header.svg?no-inline'
-import userAvatar from '../../assets/person.svg?no-inline'
 import { useSystemState } from '../../composables/useSystemState.js'
 import { recognizeOcrFiles } from '../../services/ocr.js'
 import { runOrchestrator } from '../../services/orchestrator.js'
 
+const aiAvatar = '/assets/header.png'
+const userAvatar = '/assets/person.png'
+
 const SOURCE_LABELS = {
   workbench: '来自个人工作台',
   topbar: '来自发起报销',