Respect startup update-check config

[GreyforgeLabs]

Description

Respects the existing check_for_update_on_startup config flag before starting background update checks in both CLI command mode and TUI startup.

The typed engine config already loads this field from config.toml, but the startup paths were not consulting it:

• non-TUI CLI commands always spawned check_for_updates_background()
• the TUI always spawned an UpdateManager::check_update() task

With this change, setting check_for_update_on_startup = false prevents those startup update checks.

Related Issue

Fixes PlatformNetwork/bounty-challenge#50048

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Performance improvement
• Code refactoring

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Testing

cargo check -p cortex-cli --no-default-features --features cortex-tui

Note: full default-feature check in this local environment is blocked by missing system alsa.pc for alsa-sys; the no-audio check covers cortex-cli and cortex-tui compilation for this patch.