## Summary
* **What is the goal of this PR?** Fixes a bug -
https://github.com/daveallie/crosspoint-reader/issues/187 - where the
screen would freeze after entering a WiFi password, causing the device
to appear hung.
* **What changes are included?**
- Fixed a race condition in `WifiSelectionActivity::displayTaskLoop()`
that caused rendering of an empty screen when transitioning from the
keyboard subactivity
- Added `vTaskDelay()` when a subactivity is active to prevent CPU
starvation from a tight `continue` loop
- Added a check to skip rendering when in `PASSWORD_ENTRY` state,
allowing the state machine to properly transition to `CONNECTING` before
the display updates
## Additional Context
* **Root cause:** When the keyboard subactivity exited after password
entry, the display task would wake up and attempt to render. However,
the `state` was still `PASSWORD_ENTRY` (before `attemptConnection()`
changed it to `CONNECTING`), and since there was no render case for
`PASSWORD_ENTRY`, the display would show a cleared/empty buffer,
appearing frozen.
* **Performance implications:** The added `vTaskDelay(10)` calls when
subactivity is active or in `PASSWORD_ENTRY` state actually improve
performance by preventing CPU starvation - previously the display task
would spin in a tight loop with `continue` while a subactivity was
present.
* **Testing focus:** Test the full WiFi connection flow:
1. Enter network selection
2. Select a network requiring a password
3. Enter password and press OK
4. Verify "Connecting..." screen appears
5. Verify connection completes and prompts to save password
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