[codex] Refresh NetPulse with sailfish branding

[futeng]

What changed

• replace the previous complex otter/ball/network artwork with a minimal sailfish identity
• make sailfish the default animated menu bar character and migrate legacy tropical-fish settings
• show the fixed bundled sailfish logo in the dashboard header, independent of health state and macOS icon caching
• regenerate a much smaller application icon and add a reproducible icon script
• replace the dashboard screenshot and add a menu bar screenshot
• provide complete English and Simplified Chinese READMEs
• make local install/status-bar checks target the exact NetPulse process

Validation

• swift test --package-path NetPulse: 24 tests passed
• installed and launched /Users/futeng/Applications/NetPulse.app
• visually confirmed the dashboard exposes NetPulse 旗鱼 Logo
• menu bar status-item self-check passed
• Universal build contains x86_64 arm64
• strict ad-hoc code-signature verification passed
• bundled NetPulseMascot.png verified in application resources
• README image references and whitespace checks passed