refactor(theme): remove deprecated ThemeColorUtils and migrate header theming to ColorUtil

[joshtrichards]

Not sure about the fallback colors

• Removes ThemeColorUtils and all related usages from DrawerActivity, ToolbarActivity, and dependency injection modules.
• Migrates header and icon theming to use ColorUtil with tone-based contrast logic for improved visual consistency and maintainability.
• Cleans up DI modules and deletes redundant code.

And addresses these lint warnings:

w: file:///home/runner/work/android/android/app/src/main/java/com/nextcloud/client/di/ThemeModule.kt:13:8 'class ThemeColorUtils : Any' is deprecated. Deprecated in Java.
w: file:///home/runner/work/android/android/app/src/main/java/com/nextcloud/client/di/ThemeModule.kt:30:32 'class ThemeColorUtils : Any' is deprecated. Deprecated in Java.
w: file:///home/runner/work/android/android/app/src/main/java/com/nextcloud/client/di/ThemeModule.kt:30:50 'constructor(): ThemeColorUtils' is deprecated. Deprecated in Java.

Related context: PR #10717

Theming/Drawer Branding PR Test Checklist

• Drawer header background uses correct branding color (from server or fallback)
• Switching server branding colors (light, dark, saturated, invalid, unset) updates UI correctly
• App appears correct in both light and dark mode
• No crashes or rendering issues after logging into/out of Nextcloud accounts with/without branding
• Drawer and banner appearance is correct for branded and unbranded builds, and when banner is hidden by preference
• Multi-account scenarios: branding and contrast are correct per account

Optional:

• Test on multiple Android versions and screen sizes

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🖼️ Screenshots

🏚️ Before	🏡 After
B	A

🏁 Checklist

• Tests written, or not not needed

[github-actions]

Codacy

SpotBugs

Category	Base	New
Bad practice	42	42
Correctness	75	75
Dodgy code	256	256
Experimental	1	1
Internationalization	7	7
Malicious code vulnerability	2	2
Multithreaded correctness	34	34
Performance	44	44
Security	18	18
Total	479	479

[github-actions]

APK file: https://www.kaminsky.me/nc-dev/android-artifacts/16492.apk



To test this change/fix you can simply download above APK file and install and test it in parallel to your existing Nextcloud app.

[github-actions]

blue-Light-Screenshot test failed, but no output was generated. Maybe a preliminary stage failed.