feat: full-field display for message/staff/accounts (raw_json + drawers)

Replicates the Customer all-fields pattern across the remaining three
entities. Backend now exposes `raw_json` on MessageOut / StaffOut /
AccountOut so the frontend can render every 云客 source field without a
second endpoint. Each entity gains a Chinese-label field utility + an
el-drawer surfacing all fields (structured-first, raw_json fallback,
unknown keys under 其他).

Backend:
- schemas.py: add `raw_json: dict | None` to MessageOut / StaffOut /
  AccountOut. MessageOut/StaffOut pick the column up via from_attributes;
  AccountOut is built explicitly in the router, which now threads
  `raw_json` through from both WechatAccount and WhatsappAccount rows.
- tests: new raw_json serialization tests for messages, staff, accounts
  (assert populated dict round-trips verbatim + NULL serializes as null).

Frontend (yunkes/):
- New utils: messageFields.ts, staffFields.ts, accountFields.ts — each
  with a 中文 label map, ordered groups, structured-column preference,
  and an 其他 fallback for unknown raw_json keys.
- Message: clicking a chat bubble opens an all-fields drawer (referMsg
  renders as pretty-printed JSON). Image preview + file download links
  stopPropagation so their own interactions still work.
- Staff: row click → drawer; columns relabeled (员工ID, 销售手机).
- Accounts: new AccountList.vue at /accounts with a 账号 nav item,
  unified WeChat/WhatsApp table (渠道/账号ID/昵称/微信号/归属员工/好友数/
  群数/收发/在职/最后更新), channel filter, pagination, row-click drawer.
- api: add Account type + getAccounts(); add raw_json to Message/Staff.

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

yunkes/src/api/index.ts

@@ -5,6 +5,7 @@
 // (the backend treats missing as "no filter").
 import { getJson } from './client'
 import type {
+  Account,
   CallChannel,
   Channel,
   Customer,
@@ -102,6 +103,24 @@ export function getStaff(query: StaffQuery = {}): Promise<Page<Staff>> {
   )
 }
 
+export interface AccountQuery {
+  /** channel filter; `'all'` (default) drops the param so both channels union. */
+  channel?: Channel | 'all'
+  page?: number
+  page_size?: number
+}
+
+export function getAccounts(query: AccountQuery = {}): Promise<Page<Account>> {
+  return getJson<Page<Account>>(
+    '/accounts',
+    clean({
+      channel: query.channel === 'all' ? undefined : query.channel,
+      page: query.page ?? 1,
+      page_size: query.page_size ?? 20,
+    }),
+  )
+}
+
 // ---------------------------------------------------------------------------
 // Chat groups
 // ---------------------------------------------------------------------------
@@ -197,6 +216,7 @@ export function getSyncStatus(): Promise<SyncStatus> {
 }
 
 export type {
+  Account,
   CallChannel,
   Channel,
   Customer,