feat(db): support full paper fetching

[chengzr01]

Closes #423

📑 Description

✅ Checks

• My pull request adheres to the code style of this project
• My code requires changes to the documentation
• I have updated the documentation as required
• All the tests have passed
• Branch name follows type/descript (e.g. feature/add-llm-agents)
• Ready for code review

ℹ Additional Information

[codecov]

Codecov Report

Attention: Patch coverage is 92.47312% with 7 lines in your changes missing coverage. Please review.

Project coverage is 90.53%. Comparing base (cef4c05) to head (e144a32).
Report is 1 commits behind head on main.

@@            Coverage Diff             @@
##             main     #437      +/-   ##
==========================================
+ Coverage   90.49%   90.53%   +0.04%     
==========================================
  Files          56       56              
  Lines        2377     2462      +85     
==========================================
+ Hits         2151     2229      +78     
- Misses        226      233       +7     

Files	Coverage Δ
research_town/dbs/db_paper.py	97.22% <ø> (ø)
tests/utils/test_paper_collector.py	100.00% <100.00%> (ø)
research_town/utils/paper_collector.py	93.39% <91.25%> (-6.61%)	⬇️

[lwaekfjlk]

LGTM!