feat: Bandwidth limiting

[Snider]

Summary

Limit download bandwidth to avoid saturating connection.

Use Case

• Don't max out shared internet
• Be nice to source servers
• Background collection without impact

Commands

# Limit to 1 MB/s
borg collect github repos org --bandwidth 1MB/s

# Limit to 500 KB/s
borg collect website https://example.com --bandwidth 500KB/s

# Unlimited (default)
borg collect website https://example.com --bandwidth 0

Units

• KB/s - Kilobytes per second
• MB/s - Megabytes per second
• Mbps - Megabits per second

Configuration

bandwidth:
  global: 5MB/s           # Total across all connections
  per_connection: 1MB/s   # Per individual download
  
# Time-based limits
schedule:
  - time: "09:00-17:00"
    bandwidth: 1MB/s      # Work hours: low
  - time: "17:00-09:00"  
    bandwidth: 10MB/s     # Off hours: high

Implementation

Token bucket for bandwidth allocation.

Acceptance Criteria

• Global bandwidth limit
• Per-connection limit
• Human-readable units
• Scheduled limits
• Accurate throttling

[google-labs-jules]

Jules is on it. When finished, you will see another comment and be able to review a PR.

[google-labs-jules]

Ready for a review! A PR has been created.