Fixes part of #5035: Add missing app data reset flow tests

[Sandesh282]

Explanation

Fixes part of #5035

Adds missing tests for the app data reset flow from PR #4418.

• PinPasswordActivityTest (6 tests): covers the admin forgot-PIN → data reset dialog flow, including confirmation/cancel dialogs, profile deletion + activity finishing, and locale preservation after reset.
• SplashActivityTest (2 tests): verifies the splash activity routes to onboarding and re-initializes locale correctly after a data reset.

Essential Checklist

• The PR title starts with "Fix #bugnum: " (If this PR fixes part of an issue, prefix the title with "Fix part of #bugnum: ...".)
• The explanation section above starts with "Fixes #bugnum: " (If this PR fixes part of an issue, use instead: "Fixes part of #bugnum: ...".)
• Any changes to scripts/assets files have their rationale included in the PR explanation.
• The PR follows the style guide.
• The PR does not contain any unnecessary code changes from Android Studio (reference).
• The PR is made from a branch that's not called "develop" and is up-to-date with "develop".
• The PR is assigned to the appropriate reviewers (reference).

[github-actions]

Coverage Report

Results

Number of files assessed: 2
Overall Coverage: 0.00%
Coverage Analysis: PASS ✅

Exempted coverage

Files exempted from coverage

File	Exemption Reason
SplashActivity.kt app/src/main/java/org/oppia/android/app/splash/SplashActivity.kt	This file is incompatible with code coverage tooling; skipping coverage check.
PinPasswordActivity.kt app/src/main/java/org/oppia/android/app/profile/PinPasswordActivity.kt	This file is incompatible with code coverage tooling; skipping coverage check.

Refer test_file_exemptions.textproto for the comprehensive list of file exemptions and their required coverage percentages.

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