Feature request: Add bookmarks feature (personal pins)

[zomglings]

Summary

It would be useful to have a bookmarks feature in clacks - similar to Slack's "Save for later" or personal pins functionality.

Use Case

When reading through channels or threads, users often come across messages they want to reference later. A bookmarks feature would allow:

• Saving important messages locally for quick retrieval
• Organizing saved messages (e.g., by topic, project, or custom tags)
• Listing and searching through bookmarked messages

Proposed Commands

# Save a message
clacks bookmark add -c "#channel" -m "1234567890.123456"
clacks bookmark add -c "#channel" -m "1234567890.123456" --tag "important"

# List bookmarks
clacks bookmark list
clacks bookmark list --tag "important"

# Remove a bookmark
clacks bookmark remove -m "1234567890.123456"

Notes

This could be stored locally (e.g., in a SQLite database or JSON file alongside the existing config) rather than using Slack's native saved items API, giving users full control over their bookmarks.