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/lib/document-versioning.test.ts

@@ -153,6 +153,25 @@ describe("parseVersionUploadForm", () => {
     form.append("fields", '{"a":1}');
     expect(parseVersionUploadForm(form).ok).toBe(false);
   });
+
+  it("ค่าของ fields ไม่จำกัดความยาว (เอกสาร 100–200 หน้า — 2026-10-27) · key รับได้ถึง 1,000", () => {
+    const big = baseForm();
+    big.append("fields", JSON.stringify({ detail1: "พ".repeat(1_000_000) }));
+    expect(parseVersionUploadForm(big).ok).toBe(true);
+
+    const manyKeys = baseForm();
+    manyKeys.append(
+      "fields",
+      JSON.stringify(Object.fromEntries(Array.from({ length: 1_000 }, (_, i) => [`tag${i}`, "x"]))),
+    );
+    expect(parseVersionUploadForm(manyKeys).ok).toBe(true);
+    const over = baseForm();
+    over.append(
+      "fields",
+      JSON.stringify(Object.fromEntries(Array.from({ length: 1_001 }, (_, i) => [`tag${i}`, "x"]))),
+    );
+    expect(parseVersionUploadForm(over).ok).toBe(false);
+  });
 });
 
 describe("sanitizeDisplayFileName / sanitizeFilePartName", () => {