Rebrand as Lumen Browser and repair space gestures

[Andresshamis]

Summary

• make last-space swipe routing deterministic and support rapid chained creation gestures
• fix clipping in the space-creation progress indicator
• rebrand the application and documentation as Lumen Browser
• replace the legacy app icon with the light/dark Apple Icon Composer asset and correct light-mode translucency tinting
• preserve legacy bundle, data, and keychain compatibility where required

Validation

• swift test (425 tests passed)
• bash -n script/build_and_run.sh
• ./script/build_and_run.sh --verify
• git diff --check