🧪 Test Case: Secure Background Scanning Verification (v1.0.3)

### 🎯 Goal
Verify that background scanning operates securely — the app records WiFi/Bluetooth scans with GPS data in the database while in the background, and the passphrase is only cached during active scanning.

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### ✅ Test Checklist
- [ ] Start a WiFi/Bluetooth scan in the app.
- [ ] Send the app to the background (press **Home** or switch to another app).
- [ ] Move to different locations for several minutes to generate GPS data.
- [ ] Return to the app.
- [ ] Stop the scan.
- [ ] Check the database for new scan entries recorded during the background period.
- [ ] Confirm GPS coordinates and timestamps are present in the new entries.
- [ ] After stopping the scan, verify that the passphrase is cleared from memory.
- [ ] Confirm the unlock dialog appears when reopening the app after stopping the scan.
- [ ] Ensure app content is hidden by a black overlay until the passphrase is re-entered.

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### 🧾 Expected Results
- WiFi/Bluetooth scans and GPS data are successfully recorded while the app runs in the background (if scanning is active).
- Passphrase remains cached **only** during active scanning.
- Passphrase is cleared and re-entry required once scanning stops or the app is closed.
- App content remains hidden behind the black overlay until successful unlock.

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### 🧭 Notes
- Test on multiple devices and Android versions if possible.
- Report any cases where scans are missing, GPS data is incomplete, or the security overlay/passphrase logic fails.

Start with the Android app and run the checklist on a device: begin a WiFi/Bluetooth scan, background the app, move to collect GPS data, then stop scanning. Inspect the database for entries, coordinates, and timestamps, and verify passphrase clearing, the unlock dialog, and the black overlay; repeat on additional Android versions if possible.

Written by the indexing model from the issue text.