🛡️ Sentinel: [security improvement] Disable app backups and cleartext traffic

[LeanBitLab]

🚨 Severity: MEDIUM
💡 Vulnerability: The app implicitly allowed backups (allowBackup="true" by default) and cleartext traffic (on older APIs), which could expose sensitive data like cached Reddit OAuth tokens through physical device backups or MITM network attacks.
🎯 Impact: An attacker with physical access could use adb backup to extract OAuth tokens and browse data. Without enforced HTTPS, network traffic might be intercepted on older APIs.
🔧 Fix: Explicitly set android:allowBackup="false" and android:usesCleartextTraffic="false" in AndroidManifest.xml. Also resolved a compiler conflict with androidx.compose.ui.semantics.Role in MinimalButton.kt and an API level lint error in themes.xml.
✅ Verification: Ran ./gradlew test and ./gradlew lint successfully.

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PR created automatically by Jules for task 6680996972366352926 started by @LeanBitLab

[google-labs-jules]

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