IDEA: add search from external source feature

[tnkshuuhei]

Paper Search MC

• Google Scholar
• CiNii Articles
• J-STAGE
• 学術機関リポジトリ（IRDB）
• Semantic Scholar
• BASE
• CORE
• Science.gov
• Baidu Scholar
• RefSeek
• PLOS
• PubMed
• IEEE Xplore®Digital Library

[tnkshuuhei]

We use Semantic scholar api instead of paper search mcp because it's kinda tricky to run mcp written in python on nextjs/mastra environment #191