fix(docver): drop fields value limit + treat history 404 as empty in add-in

Two fixes from first real-Word testing of the unmocked versioning flow:

- fields value length: remove the limit entirely (was 10,000, briefly
  100,000) — real court documents run 100-200 pages with content
  controls several hundred thousand chars long; callers are Bearer-only
  and the column is Postgres jsonb (up to ~255MB), so no storage
  bottleneck. Structural guards stay: ≤1,000 keys (was 100), key ≤200
  chars, value must be string.
- getVersions in versioningService now maps the history 404 to an empty
  list: files stamped SavedByAddIn back in the mock era enter the
  tracking phase before any real upload exists, so the pane shows
  "ยังไม่มี version ในระบบ" and Save & Version creates v1 (implicit
  document creation) instead of surfacing a 404 error banner. Other
  errors still propagate.

Tests: 288/288 (new cases — 1M-char value passes, key cap 1,000/1,001,
history 404 -> []). E2E against MinIO: 50k and 1M-char Thai field values
upload 200 and roundtrip byte-exact through jsonb. Docs synced:
PLAN-DOCVER §1, CLAUDE.md.

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

tests/wordaddin/versioningService.test.ts

@@ -162,6 +162,18 @@ describe("versioningService (real mode)", () => {
     vi.stubGlobal("fetch", vi.fn(async () => new Response("{}", { status: 401 })));
     await expect(getVersions("d")).rejects.toMatchObject({ name: "AuthRequiredError" });
   });
+
+  it("404 จาก history (เอกสารยังไม่เคยมี version เช่น stamp ค้างสมัย mock) = list ว่าง ไม่ใช่ error", async () => {
+    await signInReal();
+    vi.stubGlobal(
+      "fetch",
+      vi.fn(
+        async (_url: string, _init?: RequestInit) =>
+          new Response(JSON.stringify({ error: "ไม่พบเอกสารนี้ในระบบ (ยังไม่เคยอัปโหลด version)" }), { status: 404 }),
+      ),
+    );
+    await expect(getVersions("d")).resolves.toEqual([]);
+  });
 });
 
 // โหมด demo ไว้ท้ายสุด — signInForDemo เปิด flag ค้างใน module จนกว่าจะ sign-in จริง