feat: add auto-kill rules for idle ports

[productdevbook]

Summary

• Configurable auto-kill rules that terminate processes after a timeout
• Rules match by process name pattern (glob with * wildcard) and/or port number
• Timeout configurable from 1 to 1440 minutes (24 hours)
• Optional notification before killing
• Per-rule enable/disable toggle
• Settings UI with add/edit/delete rule management
• Rules checked on every port scan cycle

Example Rules

• "Kill idle Node.js after 30 min" — Process: node*, Timeout: 30 min
• "Kill port 8080 after 1 hour" — Port: 8080, Timeout: 60 min

Closes #30

Test plan

• Add a new auto-kill rule in Settings > Auto-Kill Rules
• Set process pattern (e.g. node*) and timeout
• Verify process matching works (start a matching process)
• Verify process is killed after timeout expires
• Verify notification appears when notifyBeforeKill is enabled
• Edit existing rules via pencil icon
• Delete rules via trash icon
• Disable a rule and verify it no longer triggers
• Rules with empty pattern AND port 0 cannot be saved

🤖 Generated with Claude Code