feat: LLM 论文图书馆 — 初始提交

- FastAPI 后端: REST API + Bearer Token 鉴权 + PDF 代理
- 180 篇论文数据 (data/papers.json): 9 模块、32 子领域
- 前端: 数据驱动、卡片径向渐变光效、PDF 页面内阅读
- 底部状态栏: arXiv/HF 连通性检测
- PDF 加载: arXiv 优先(5s超时) → HK 本地兜底
- Docker 化部署 (Dockerfile + start.sh + nginx.conf)
- arXiv + HF 批量下载器 (api/downloader.py)

api/backfill.py

@@ -0,0 +1,57 @@
+#!/usr/bin/env python3
+"""Backfill all uncached PDFs, skipping dead arXiv IDs"""
+import json, subprocess, sys, time
+from pathlib import Path
+
+PAPERS_JSON = Path(__file__).resolve().parent.parent / "data" / "papers.json"
+ARXIV_DIR   = Path(__file__).resolve().parent.parent / "papers" / "arxiv"
+LOG_FILE    = Path("/app/papers/backfill.log")
+
+def main():
+    with open(PAPERS_JSON) as f:
+        data = json.load(f)
+
+    # Collect all arxiv IDs
+    arxiv_ids = set()
+    for mod in data.values():
+        for area in mod.get("areas", []):
+            for section in ("mainline", "branches", "forward"):
+                for p in area.get(section, []):
+                    aid = p.get("arxiv")
+                    if aid:
+                        arxiv_ids.add(aid)
+
+    cached = {p.stem for p in ARXIV_DIR.glob("*.pdf")}
+    missing = [aid for aid in arxiv_ids if aid not in cached]
+    print(f"Total: {len(arxiv_ids)}, Cached: {len(cached)}, Missing: {len(missing)}")
+
+    if not missing:
+        print("All caught up!")
+        return
+
+    ok, fail = 0, 0
+    for aid in missing:
+        url = f"https://arxiv.org/pdf/{aid}.pdf"
+        dest = ARXIV_DIR / f"{aid}.pdf"
+        try:
+            r = subprocess.run(
+                ["wget", "-q", "-T", "15", "-O", str(dest), url],
+                timeout=20
+            )
+            if r.returncode == 0 and dest.exists() and dest.stat().st_size > 5000:
+                ok += 1
+                print(f"  OK  {aid}  ({dest.stat().st_size//1024} KB)")
+            else:
+                dest.unlink(missing_ok=True)
+                fail += 1
+                print(f"  FAIL {aid}  (rc={r.returncode}, sz={dest.stat().st_size if dest.exists() else 0})")
+        except Exception as e:
+            dest.unlink(missing_ok=True)
+            fail += 1
+            print(f"  ERR {aid}  {e}")
+        time.sleep(0.8)  # Be nice to arXiv
+
+    print(f"\nDone: {ok} ok, {fail} failed")
+
+if __name__ == "__main__":
+    main()