Add Privacy Lock for Specific Groups (Password/Biometric)

Checklist

• I've already searched in existing issues and haven't found a similar feature request.

Which category best fits this feature request?

Feed Sync & Management

Is your feature request related to a problem? Please describe.

📝 Feature Description

I would like to request an optional Privacy Lock feature for RSS Groups within the ReadYou application.

When this feature is enabled for a group, the user must successfully authenticate using a password, fingerprint (Biometric), or face recognition before they can view any feeds or articles belonging to that specific group. This is crucial for groups containing sensitive content, such as NSFW material, to protect user privacy from casual viewing.

✨ Motivation

• Enhanced Privacy Protection: It allows users to safely subscribe to and read RSS feeds containing sensitive content without the worry of them being accidentally seen by family, friends, or colleagues.
• Improved User Experience: This is a common privacy feature in many content aggregation apps, helping to better meet the diverse needs of the user base.

Describe the solution you'd like

The proposed solution is to introduce a configurable Privacy Lock option for individual RSS groups, enforced by biometric authentication (fingerprint/face) or a fallback password.

Implementation Goals:

• Group Setting Toggle: Add an option in the group settings to enable the Privacy Lock.
• Biometric First: Prioritize using the device's Biometric API for quick unlocking.
• Access Control: Require successful authentication when a user attempts to open a locked group.
• Content Hiding: Articles belonging to a locked group should be hidden or blurred in the main aggregated feeds ("All Articles," "Unread Articles") until the group is unlocked.
• Auto-Lock: The lock should re-engage when the app is backgrounded or after a set idle time.

Related links

No response

No files, tests, or entry points are identified in the issue, so start by locating group settings, article aggregation, and the app's existing biometric or authentication handling. Done would include per-group locking, protected content in aggregate views, biometric or password access, and relocking after backgrounding or the configured idle period.