Download files from subdirectories in /data

[claymore666]

Summary

Fixes #30

• Recursively download all files from /data directory including subdirectories
• Preserve directory structure locally (e.g., /data/logs/syslog → ./data/wt-xxx/logs/syslog)
• Exclude /data/swap/ and /data/lost+found/ directories from downloads
• Automatically create local subdirectories as needed

Changes

Recursive file discovery

• Use find command to recursively discover all files in /data
• Filter out swap and lost+found directories
• Maintain relative paths for proper local directory structure

Download improvements

• Calculate relative paths from /data to preserve directory structure
• Create local subdirectories automatically with os.makedirs()
• Hash comparison works with files in subdirectories

Test plan

• Test downloading files from subdirectories: ceti whaletag -t wt-b827eb123456
• Verify /data/logs/syslog files are downloaded to ./data/wt-xxx/logs/syslog
• Verify swap and lost+found directories are excluded
• Verify directory structure is preserved locally