Feature request: Support image/file uploads in clacks send

[zomglings]

Feature Request

Add support for uploading images and files via clacks send.

Use Case

When using clacks as a bridge for Claude Code to respond via Slack, it's useful to send generated charts, screenshots, or other files. Currently there's no way to upload files - only text messages are supported.

Proposed API

# Upload a file
clacks send -c "#channel" -f /path/to/image.png

# Upload with a message
clacks send -c "#channel" -m "Here's the chart" -f /path/to/chart.png

# Multiple files
clacks send -c "#channel" -f file1.png -f file2.png

Context

This came up while building a Slack-to-Claude Code bridge where Claude generates matplotlib charts but can't send them back to Slack.

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🤖 Generated with Claude Code