Hardcoded memory defaults in launch and TUI display instead of using config defaults

[X12101XX]

what happened

The launch funciton and TUI settings display use hardcoded strings 512M" and "2G" as memory fallbacks instead of reading from the global config defaults.

This means:

• Changing defaults in config.toml has no effect on the TUI display when an instances's memory fiedlds ar null.
• The lanch fallback and the TUI display use different values if someone changes only one of the two locations.

steps to reproduce

1. Set memory_max = "4G" in config.toml
2. Create a new instance (memory_max will be null)
3. Check TUI settings display, find that the memory_max is "2G"

rmcl version

0.3.0

operating system

Linux

additional context

Proper Fix: replaced hardcoded strings with &crate::config::SETTINGS.defaults.memory_min/max

(This issue was written with AI assistance for English translation.)