Improve connection feedback and status indication for external GPS receiver

Nobody has claimed this yet.

Description
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Two related UX issues have been identified in the external GPS receiver connection flow that can mislead the user into believing a connection has been successfully established when it has not.

**Issue 1 — Missing feedback when user closes the connection pop-up (Path A)**
When connecting to a network receiver, the following pop-up appears:
_"Connecting to external receiver. Connecting to TCP/IP and Port. You can close this panel, the app will continue in the background."_
**There are two distinct paths after this dialog appears:**
- Path A — User taps X (closes the pop-up):
The dialog closes silently. No error or warning message is shown. The user receives no feedback that the connection attempt failed or was interrupted. When returning to the receiver list, the user may see a green circle on the selected device and incorrectly assume the connection succeeded.

- Path B — User waits (~5 seconds):
The app completes the timeout and displays an error message indicating the connection could not be established, giving the user clear and actionable feedback.

**Issue 2 — Misleading green circle on failed connection**

- The selected receiver is marked with a green circle regardless of the actual connection status — including when the connection has failed and the app displays "No connection, reconnecting...". Users may mistake the green circle with a specific symbol as an indicator of a successful connection rather than understanding it only marks the selected receiver.

Actual Result
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**Issue 1:**

- Path A (X button): dialog closes silently with no feedback — the user has no way of knowing whether the connection succeeded or failed
- Path B (wait for timeout): error message is displayed correctly
**Issue 2:**

- The green circle with a specific symbol indicator is intended to mark only the selected receiver, not the connection status. However, its appearance is identical regardless of whether the connection succeeded or failed — including during active failure states such as "No connection, reconnecting..." — making it **visually indistinguishable** from a successful connection state

Expected Result
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**Issue 1:**

- When the user closes the connection pop-up via the X button (Path A), the app should display an appropriate feedback message informing the user that the connection attempt was interrupted or has not yet been confirmed
- The feedback should be consistent with the error message displayed in Path B after the timeout completes
- The user should never be left without feedback about the connection status after closing the dialog

**Issue 2:**

The green circle indicator should clearly distinguish between selected and connected states:
- This ensures the user always has an accurate understanding of the current connection status

Screenshot:
Manage GPS receiver

Start at the external GPS receiver connection flow, focusing on the pop-up's X-button and timeout handling. Then inspect how the receiver list chooses the green-circle indicator for selected and failed connections. Done means closing the pop-up provides feedback and the indicator distinguishes selection from an active connection failure.

Written by the indexing model from the issue text.