[Feature]allow Feishu to config where to save recived files

[szyhf]

🎯 The Goal / Use Case

Refactor Feishu channel file download mechanism with improved organization and intelligent deduplication.

💡 Proposed Solution

Directory Structure Simplification:

• Changed from hash-based paths to human-readable structure: {download_dir}/{year}/{month}/{filename}
• Files are now organized by time (e.g., downloads/2026/03/report.pdf)
• Preserves original filenames with comprehensive character sanitization

Intelligent Deduplication:

• Smart hash-based deduplication only checks when same-month + same-filename conflicts occur
• Same hash + size → reuse existing file (avoid duplicate downloads)
• Different hash/size → auto-generate suffix (file-1.pdf, file-2.pdf)

Lightweight Directory Indexing:

• Each directory has its own .feishu_index.json for metadata tracking
• Records file hash, size, Feishu file_key, message_id, and download time
• Enables file re-downloading if local files are lost
• Independent indexes minimize impact of corruption

Configurable Read-Only Protection:

• New config field download_readonly_disable (default: false)
• When disabled (default), downloaded files are set to read-only (0o444) to prevent accidental modification
• Users can enable editing by setting download_readonly_disable: true

🛠 Potential Implementation (Optional)

I already make it done, and I'll make a PR

🚦 Impact & Roadmap Alignment

• This is a Core Feature
• This is a Nice-to-Have / Enhancement
• This aligns with the current Roadmap

🔄 Alternatives Considered

💬 Additional Context

[axwfae]

It is recommended that all chennls directories should have this design to prevent the files in the workspace directory from becoming increasingly complex and unmanageable! Currently, picoclaw places all files in the workspace directory, which is a very poor design! It is recommended to add workspace/tmp, workspace/download, and workspace/chennls directories to accommodate different applications!

The workspace/tmp directory is used to store temporary documents or files!

The workspace/download folder contains files downloaded from the internet.

The workspace/chennls directory stores files transferred from chennls, such as discond files or telegrams. If multiple chenns directories are used simultaneously, additional partitions can be created, such as qq, discond, etc.