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_web.md

@@ -10,6 +10,9 @@ The format loosely follows Keep a Changelog and can be adapted to the team's hab
 
 ### Added / 新增
 
+- Library uploads over 16MB now auto-switch to the resumable chunked protocol (8MB parts): failed parts retry in place up to 3 times and already-sent parts are skipped, so a flaky upload continues instead of starting over; small files keep the original single request.
+- 书库上传超过 16MB 自动切换为可续传分片协议（每片 8MB）：失败的分片原地重试至多 3 次，已传片自动跳过，中断后继续而不是从头再来；小文件仍走原单次上传。
+
 - Immersive reading for text & comics (微信读书/Mihon-style): tap the middle of the page to show/hide the reader header and control bar; controls now live in a slide-up bottom sheet — a progress slider jumps to any position (text) or page (CBZ), theme swatches (纸/米/夜) are WYSIWYG color dots, plus A−/A+ font size; body text is serif with a readable justified measure; all prefs persist (localStorage).
 - 文本与漫画进入沉浸阅读:点正文中央唤出/隐藏顶栏与工具条;控件收进底部滑出抽屉——进度/页码滑条直接跳到全书任意位置或任意页,主题改为所见即所得的色卡(纸/米/夜),保留 A−/A+ 字号;txt/md 正文为衬线、限宽两端对齐;偏好本地持久化。
 - CBZ adds reading modes — 连读 (continuous scroll) / 整页 (snap to page top) / 适高 (one page per screen, full width) — cycle button in the bar, choice remembered; tapping the left/right edges turns a page/screen and ←/→/PageUp/PageDown work too.