fix(samples): Make Nav2 sample dark-mode compatible

[0xadam-brown]

📜 Description

Resolve the remaining light-only colors in the Nav2 sample so the view and Compose paths follow the active DayNight theme.

Replace fixed black and white surfaces and text with theme-derived colors, and let the Compose hosts render their own themed backgrounds instead of forcing white containers.

💡 Motivation and Context

Follow-up to @runningcode's comment here.

💚 How did you test it?

📝 Checklist

• I added GH Issue ID & Linear ID
• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• I updated the wizard if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.
• No breaking change for hybrid SDKs or communicated to hybrid SDKs.
• Public API changes reviewed by another Mobile SDK team member or implemented according to the develop docs spec.

🔮 Next steps

#skip-changelog

[sentry]

📲 Install Builds

Android

🔗 App Name	App ID	Version	Configuration
SDK Size	io.sentry.tests.size	8.55.0 (1)	release

⚙️ sentry-android Build Distribution Settings

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[runningcode]

oh nice! color theme is mostly bike shedding but thanks for fixing it!