[codex] Update project settings and remove UI tests

[crazytan]

What changed

• updated the Xcode project generation settings to the latest local Xcode compatibility level
• enabled dead code stripping and added stricter project-wide build settings
• moved app versioning to MARKETING_VERSION and CURRENT_PROJECT_VERSION
• documented local signing overrides in Config.xcconfig.example
• removed the broken TaskMenuUITests target and deleted its source file

Why

• keeps the generated project aligned with the current Xcode toolchain
• tightens release settings with DEAD_CODE_STRIPPING, -Osize, and warnings-as-errors
• avoids carrying a known-broken UI test target that was causing build and test churn

Impact

• the app and unit-test targets still build and test successfully
• UI tests are no longer part of the project
• local signing remains configurable through the ignored Config.xcconfig

Validation

• xcodebuild -scheme TaskMenu -configuration Debug build
• xcodebuild -scheme TaskMenu -configuration Debug test