fix: Fix failing very first wifi connection attempt (#1521)

## Summary

* **What is the goal of this PR?** The very first Wifi connection
attempt with saved credentials failed, subsequent attempts succeeded.
This PR fixes the first-attempt-issue.
* **What changes are included?**

## Additional Context
Claude analysis for WifiSelectionActivity

In attemptConnection() ,there's no WiFi.disconnect() before WiFi.begin()
— unlike the scan path earlier which does do a disconnect first.

The root cause on ESP32 is the built-in auto-connect feature: the ESP32
WiFi stack saves credentials to NVS flash and automatically starts
trying to connect on boot before your application code runs. When your
attemptConnection() then calls WiFi.begin(), the stack is already in a
transitional CONNECTING state, and the new begin() call either gets
ignored or collides with the in-progress attempt.

The fix is to add WiFi.disconnect(true) + a short delay in
attemptConnection() before calling WiFi.begin(), and optionally call
WiFi.persistent(false) to stop the ESP32 from auto-connecting on its
own.

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