feat: vue3 frontend scaffold + org tree + customer list + chat timeline

M5b viewing frontend for the yunke data-mirror, under yunkes/.

- Scaffold: Vite + Vue 3 + TS, with element-plus, @element-plus/icons-vue,
  pinia, vue-router@4, axios. Dev server on :5173 with /api and /api/media
  proxied to the FastAPI backend on :8000.
- API client (src/api/): axios instance (baseURL '/api') whose response
  interceptor unwraps the axios envelope; typed wrappers (getCustomers,
  getMessages, getDepartments, getStaff) returning Page<T> / arrays; types
  mirroring the backend *Out schemas (Message typed as a permissive superset
  so file_th_url/duration/transcription_text degrade gracefully today and
  light up once MessageOut exposes them).
- Layout: el-header top bar (title + channel switch) + el-aside department
  tree (built from the flat parent_id list via useOrgStore, with search
  filter) + el-main router-view.
- CustomerList (/customers): el-table with channel filter, department filter
  driven by the tree selection (route query), pagination, and row-click into
  the chat timeline (channel + owner_account_id + talker_id).
- ChatTimeline (/chat/:channel/:ownerId/:talkerId): asc-ordered message
  bubbles keyed by is_send (direction) and type (text/image/video/voice/file/
  divider/system/unknown); lands on the most-recent page and prepends older
  pages via load-more with scroll anchoring.
- Home '/' redirects to '/customers'.

npm run build (vue-tsc -b + vite build) is clean.

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

yunkes/src/utils/tree.ts

@@ -0,0 +1,54 @@
+import type { Department } from '@/api/types'
+
+/**
+ * Tree node consumed by `<el-tree :data>`. Element Plus looks at `label` for
+ * the text and `children` for sub-nodes (both configurable via props).
+ */
+export interface DeptTreeNode {
+  dept_id: string
+  label: string
+  raw: Department
+  children: DeptTreeNode[]
+}
+
+/**
+ * Build a department forest from the backend's flat `parent_id` list.
+ *
+ * - Roots = departments with no `parent_id` (or whose parent is missing).
+ * - Children are sorted by `path` then `dept_id` to mirror the backend ordering
+ *   (the API already returns ordered by path, but orphans re-ordering is cheap
+ *   insurance).
+ * - Falls back gracefully on cycles / dangling parent_ids (orphans become roots
+ *   rather than disappearing).
+ */
+export function buildDeptTree(departments: Department[]): DeptTreeNode[] {
+  const nodes = new Map<string, DeptTreeNode>()
+  for (const d of departments) {
+    nodes.set(d.dept_id, {
+      dept_id: d.dept_id,
+      label: d.name?.trim() || d.dept_id,
+      raw: d,
+      children: [],
+    })
+  }
+
+  const roots: DeptTreeNode[] = []
+  for (const d of departments) {
+    const node = nodes.get(d.dept_id)!
+    const parent = d.parent_id ? nodes.get(d.parent_id) : undefined
+    if (parent) {
+      parent.children.push(node)
+    } else {
+      roots.push(node)
+    }
+  }
+
+  const sortRec = (list: DeptTreeNode[]) => {
+    list.sort((a, b) =>
+      (a.raw.path ?? a.dept_id).localeCompare(b.raw.path ?? b.dept_id),
+    )
+    for (const n of list) sortRec(n.children)
+  }
+  sortRec(roots)
+  return roots
+}