ci: add Android-aware CodeQL analysis

[Anthonyy232]

Summary

• add CodeQL scanning for GitHub Actions and Java/Kotlin
• use a manual Android Gradle build because GitHub's default Java autobuild selects the nonexistent testClasses task
• pin every workflow action to an immutable commit
• run scans on pull requests, master pushes, and weekly
• make the existing release workflow token read-only by default, retaining write access only for the release job

Validation

• normal unit CI passed
• CodeQL Actions and Java/Kotlin analysis both passed with the replacement workflow
• the initial scan identified two medium missing-permissions findings in the release workflow; this branch fixes both

[github-advanced-security]

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