Refactor: Resolve TODOs in CommonsApplication and preserve UI settings on logout

[Kota-Jagadeesh]

Description (required)

Fixes #6612
Part of issue #6508

This PR addresses two long-standing TODO items in CommonsApplication.kt:

1. Fresco Initialization Cleanup: Replaced the "band-aid" try-catch block during Fresco initialization with an explicit check for the robolectric environment. This prevents the app from attempting to load native libraries in test environments where they are unavailable, fulfilling the TODO for test builds.

2. Smart Preference Clearing: Fixed the "preference manager" TODO by refactoring clearApplicationData. Instead of a total wipe using clearAll(), the app now captures the user's Theme (KEY_THEME_VALUE) and App UI Language (APP_UI_LANGUAGE) preferences before clearing data, and restores them immediately after. This ensures that visual and accessibility preferences are persistent across logout/login sessions, improving user experience.

Tests performed (required)

Tested prodDebug on Redmi Note 13 Pro 5g with API level 35.

• Unit Tests: Verified that ./gradlew test passes and that Fresco initialization is correctly skipped in the Robolectric environment.
• Manual Verification:
  1. Set the app theme to "Dark" and language to a non-default option.
  2. Performed a logout.
  3. Confirmed the Login screen remained in "Dark" mode and retained the selected language.
• Data Integrity: Verified that sensitive user data (cookies and session) are still successfully cleared.

[github-actions]

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