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>

docs/PLAN-DOCVER.md

@@ -80,7 +80,7 @@ multipart/form-data:
 | `file` | File (.docx) | บังคับ — ≤ 100MB, magic bytes `PK\x03\x04` |
 | `pdf` | File (.pdf) | optional — `size === 0` = ถือว่าไม่มี (add-in แนบ blob เปล่าได้) |
 | `clientVersionId` | string | optional ≤100 — GUID ที่ client generate เอง |
-| `fields` | string (JSON) | optional — map `{ [sdtTag]: text }` (≤100 keys, value ≤10,000) |
+| `fields` | string (JSON) | optional — map `{ [sdtTag]: text }` (≤1,000 keys · **ความยาวค่าไม่จำกัด** 2026-10-27 ตามคำขอผู้ใช้ — เอกสาร 100–200 หน้า; jsonb รับได้ถึง 255MB) |
 | `message` | string | optional — commit message ≤2048 (trim ว่าง = NULL) |
 | `fileName` | string | optional — ชื่อไฟล์ดั้งเดิม (ผ่าน `decodeUploadFilename` แล้ว) |