[lsongdev]

Summary

Change Wi-Fi from an always-on AP+STA model to an explicit provisioning lifecycle.

Normal operation

• boot in STA mode
• if saved credentials exist, start connecting immediately without blocking the rest of firmware startup
• give the saved network a 30-second startup recovery window
• remain STA-only after a successful connection
• transient runtime disconnects rely on STA auto-reconnect and do not open an AP

Setup / recovery

• start the setup AP when no credentials exist
• fall back to setup if the saved network is still unavailable after the startup window
• triple-click the printer button to request setup at any time
• saved-credential setup windows expire after five minutes
• first-boot setup remains available until configured
• use captive DNS only while setup is active
• after successful provisioning, return the HTTP response first and close the AP shortly afterward
• pause the setup timeout while a Wi-Fi connection attempt is in progress

Setup interface

While setup mode is active:

• Wi-Fi scan/connect/forget APIs are enabled
• the embedded Web UI can still print through HTTP
• raw TCP :9100 printing remains available through the temporary AP

Wi-Fi configuration APIs remain setup-only, while printing is available in both setup and normal STA operation.

Button cleanup

• replace the printer-local button state machine with lsongdev/kbutton.c
• preserve the original 40 ms debounce, 300 ms click window, and 1 s long-press timing
• double click: test page
• triple click: Wi-Fi setup
• long press/release: paper feed start/stop
• remove hal/em_button.* and its duplicated state-machine tests

The kbutton dependency is pinned to commit f0665ecca96674aa7ee033407734f0f76b386a40.