Add --level flag to spacetime logs for filtering by log level

[clockwork-labs-bot]

Fixes #1972

Adds client-side log level filtering to spacetime logs:

• --level <LEVEL> / -l <LEVEL>: Show only logs at the specified severity or higher. Valid values: trace, debug, info, warn, error, panic. Default: show all logs (no filtering).
• --level-exact: When combined with --level, show only logs at exactly the specified level.

Severity order (most to least): panic > error > warn > info > debug > trace.

Examples:

spacetime logs mydb --level warn                # Show only warn, error, and panic
spacetime logs mydb --level info                 # Show info and above
spacetime logs mydb --level error --level-exact  # Show only errors

Filtering is done client-side.