feat(addin): unmock versioning — real upload/download against docver API

Replace the in-memory versioningService with real calls to the docver
group (/api/documents/*) via apiClient with the ticket-issued Bearer;
keep the mock only for ?addindemo (authService.isDemoMode).

- uploadVersion: multipart POST /api/documents/versions (file, optional
  pdf when non-empty, clientVersionId, fields JSON, trimmed message,
  fileName) — identity fields are never sent (userId/userName/templateId
  in the form = 400 per the 2026-10-22 contract; docId comes from the
  fid claim)
- getVersions: GET → DocumentVersionDTO mapped to VersionRecord (adds
  optional createdByUserName; history panel shows it with userId
  fallback)
- getDownloadLink: GET presigned URL (+ ?format=pdf)
- apiClient.toUrl: empty NEXT_PUBLIC_ADDIN_API_BASE_URL = same-origin
  through withBasePath (/docedit/api/...); the env is now only for a
  split deployment (must include basePath, HTTPS)
- documentId/templateId params stay in signatures but are not sent
- tests: versioningService.test.ts covers both modes (real sign-in via
  signInWithTicket, FormData contract assertions, DTO mapping, format
  query, 401 -> AuthRequiredError, demo mock without network)
- docs sync: WORDADDIN-DEV (new "การรันกับ backend จริง" section),
  addin-ui-flow status note, PLAN-DOCVER §8, PLAN-ADDIN-AUTH §12, CLAUDE.md

Verified: tsc clean, 286/286 tests, full E2E against MinIO (ticket ->
token -> upload docx / docx+pdf -> history -> presigned download of both
formats).

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

wordaddin/services/apiClient.ts

@@ -1,4 +1,5 @@
 import { config } from "../config";
+import { withBasePath } from "@/utils/base-path";
 import * as authService from "./authService";
 
 /**
@@ -36,8 +37,15 @@ export interface ApiRequestOptions {
   body?: BodyInit | null;
 }
 
+/**
+ * path เต็มเสมอ — ไม่ตั้ง `NEXT_PUBLIC_ADDIN_API_BASE_URL` = same-origin ผ่าน withBasePath
+ * (ได้ /docedit/api/… ถูกต้องตาม invariant #12 — API ของกลุ่ม docver อยู่แอปนี้เอง)
+ * · ตั้งค่า = ชี้ backend คนละ origin (ต้องรวม basePath แล้ว เช่น https://host/docedit — ใช้ตอน
+ * deploy add-in กับ API คนละตัว) และต้องเป็น HTTPS เสมอ (webview ของ Word บล็อก http)
+ */
 function toUrl(path: string): string {
-  return path.startsWith("http") ? path : `${config.apiBaseUrl}${path}`;
+  if (path.startsWith("http")) return path;
+  return config.apiBaseUrl ? `${config.apiBaseUrl}${path}` : withBasePath(path);
 }
 
 async function doFetch(