Unable to connect to Bluetooth GNSS receiver after app reinstall — requires full Bluetooth re-pair as workaround

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**Description**
After reinstalling the Mergin Maps app, a previously paired Bluetooth GNSS receiver cannot be reconnected through the app's "Connect new receiver" flow. The receiver appears in the Bluetooth device list, but tapping the + button does not establish a connection and no error is shown.

**Environment**
[x] Staging [ ] PROD

**Application (+ app version, build, operating system)**
Mergin Maps Android app 2026.3.0 (RC)
Device: Redmi A3, Android 15

**Steps to reproduce**
1. Pair a Bluetooth GNSS receiver with the device and connect it successfully in the Mergin Maps app
2. Reinstall the Mergin Maps app (uninstall + install)
3. Open the app → go to GPS settings → **Connect new receiver → Bluetooth → Continue**
4. Select the same receiver from the Bluetooth device list
5. Tap the **+** button to connect

**Actual results**
No connection is established. The app gives no feedback — the receiver is not added and no error message is shown.

**Expected results**
The app should be able to reconnect to a previously OS-paired Bluetooth GNSS receiver after reinstall without requiring the user to remove and re-pair the device at the OS Bluetooth level.

**Workaround**
1. Remove the GNSS receiver from the device's Bluetooth settings
2. Re-pair the receiver at the OS level
3. Force-close the Mergin Maps app
4. Reopen the app — the receiver can now be connected via the standard flow

**Screenshots or logs**

*Conclusion*
*Created by Claude and supervised by a human test analyst.*

Start by reproducing the issue through GPS settings → Connect new receiver → Bluetooth → Continue, using the previously paired receiver after reinstall. Inspect the Android Bluetooth GNSS connection flow and the + action; done means the receiver reconnects without OS-level re-pairing and provides feedback if connection fails.

Written by the indexing model from the issue text.