Self-hosted employee directory (in-app management + CSV import)

Most sites have no external HR database, so add a self-hosted directory mode.

- New employee_directory_mode setting: 'external' (default; read a separate HR
  DB, unchanged) or 'selfhosted' (app-owned table).
- DirectoryEmployee model + directoryemployees table (migration 7d16). to_dict
  emits the same keys the external contract uses (SSO/First_Name/...), so both
  modes share one response shape and the frontend is unchanged.
- Employee search / single / batch lookup branch on the mode.
- Self-hosted-only management endpoints: list, create, update, delete, and CSV
  import (upsert by SSO). Guarded so they only work in self-hosted mode.
- EmployeeDirectory.vue management page (Settings > Locations & Organization):
  table + search + pagination, add/edit/delete, CSV import (file or paste).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/api/index.js

@@ -718,6 +718,24 @@ export const employeesApi = {
   },
   lookupMultiple(ssoList) {
     return api.get('/employees/lookup', { params: { sso: ssoList } })
+  },
+  // Self-hosted directory management (directory_mode=selfhosted)
+  directory: {
+    list() {
+      return api.get('/employees/directory')
+    },
+    create(data) {
+      return api.post('/employees/directory', data)
+    },
+    update(sso, data) {
+      return api.put(`/employees/directory/${sso}`, data)
+    },
+    remove(sso) {
+      return api.delete(`/employees/directory/${sso}`)
+    },
+    importCsv(csv) {
+      return api.post('/employees/directory/import', { csv })
+    }
   }
 }