feat(upload): resumable chunked upload protocol for large files — init(parts≤32MB)/status/complete endpoints with fingerprint-derived deterministic uploadId (same file resumes, no restart), sessions in BOOKS_DIR/.uploads with 24h sweep, frontend uploadBook auto-switches >16MB to 8MB parts (retry x3 in place, skip received); oversize single POST now reports honest 413 too_large instead of "multipart field 'file' required" (was MaxBytesReader abort mislabeled); UPLOAD_MAX_MB wired into both compose stacks (cap total, .env.example 2048), nginx body limit drops to 32m; testCfg limit 1MB, CJK/fullwidth-colon filename proven unaffected; e2e verified with 311MB real file (39 parts, sha1 match)

docs/CHANGELOG.md

@@ -8,8 +8,15 @@ The format loosely follows Keep a Changelog and can be adapted to the team's hab
 
 ## [Unreleased]
 
+### Added / 新增
+
+- API: resumable chunked upload protocol for large files — `POST /api/libraries/:id/upload/init` (fingerprint-derived deterministic `uploadId`, rejects totals over `UPLOAD_MAX_MB` with `413 too_large`), `PUT /api/uploads/:uid/parts/:index` (parts ≤ 32MB), `GET /api/uploads/:uid` (received parts, for resume), `POST /api/uploads/:uid/complete` (assemble + atomic land, same path contract as single-POST upload). Sessions persist under `BOOKS_DIR/.uploads/` with 24h opportunistic sweep. `UPLOAD_MAX_MB` is now wired through both compose stacks/`.env`; `.env.example` sets 2048 and drops `NGINX_CLIENT_MAX_BODY_SIZE` to 32m (nginx only ever sees one chunk).
+- API: 新增大文件可续传分片上传协议——`POST /api/libraries/:id/upload/init`（按指纹派生确定性 `uploadId`，总量超 `UPLOAD_MAX_MB` 返回 `413 too_large`）、`PUT /api/uploads/:uid/parts/:index`（单片 ≤32MB）、`GET /api/uploads/:uid`（查询已传分片以续传）、`POST /api/uploads/:uid/complete`（拼接后原子落盘，返回与单发上传一致的 `path`）。会话存于 `BOOKS_DIR/.uploads/`，超 24h 顺手清理。`UPLOAD_MAX_MB` 已接入两份 compose/`.env`；`.env.example` 调至 2048 并将 `NGINX_CLIENT_MAX_BODY_SIZE` 降为 32m（nginx 只见单个分片）。
+
 ### Changed / 变更
 
+- API: upload over `UPLOAD_MAX_MB` now returns `413 too_large` with the limit in the message; previously the size abort was misreported as `400 bad_request "multipart field 'file' required"`.
+- API：超过 `UPLOAD_MAX_MB` 的上传现在返回 `413 too_large` 并在消息中带上限额；此前体积超限被误报为 `400 bad_request "multipart field 'file' required"`。
 - API: `POST /api/libraries` now takes only `{name}`; `root_path` is generated server-side as `BOOKS_DIR/<sanitized name>` (no client-supplied paths, validated at creation).
 - API：`POST /api/libraries` 只需 `{name}`；`root_path` 由服务端生成为 `BOOKS_DIR/<清洗后的库名>`（不再接受客户端指定路径，创建时即校验）。
 - Repo structure conformed to `AGENTS.md`: `web/` renamed to `frontend/`; backend HTTP layer moved from `internal/api` to `cmd/webui/{api,handlers}` (`cmd/server` → `cmd/webui`); README/CHANGELOGs relocated under `docs/` (`README_zh.md` added as Chinese mirror); module-level `.gitignore`s added (`backend/`, `deploy/`); stray root `library/` removed (book files live in `deploy/api/storage/`); debug binaries untracked.