feat: company question list picker (leetcode.cn)

[fenixc9]

Summary

• Add the ability to browse and solve company interview question lists from leetcode.cn
• Users select a company from a searchable picker (e.g. 字节跳动, 腾讯, 阿里巴巴) and view that company's curated problem set
• Adds a "Company" button on the Problems page and a Leet company command
• Supports all four picker providers: fzf-lua, telescope, mini.pick, and snacks.picker
• This feature is cn-only (like the existing Hot 100 study plan picker)

API Used

Endpoint	Operation	Purpose
/graphql/noj-go	InterviewHotCompanyCards	Fetch company list (slug, name, question count)
/graphql/	favoriteQuestionList	Fetch questions for a specific company's favorite list

How it works

1. User opens the menu → Problems page → clicks "Company" (or runs :Leet company)
2. A picker displays all companies (sourced from leetcode.cn's interview company cards API)
3. User selects a company
4. The plugin fetches that company's question list via favoriteQuestionList(favoriteSlug: "{company-slug}-thirty-days")
5. Questions are filtered against the local problem cache and displayed in the standard question picker

Files Changed

File	Change
lua/leetcode-plugins/cn/queries.lua	+2 GraphQL queries
lua/leetcode/api/problems.lua	+2 API functions (company_list, company_questions)
lua/leetcode/picker/init.lua	+P.company() entry point
lua/leetcode/command/init.lua	+cmd.company() command
lua/leetcode-ui/group/page/problems.lua	+Company button
lua/leetcode/picker/company/*	+5 new files (company picker module)