Apply keypad brightness ratio immediately + drop dead UIStatus code

[brickbots]

Summary

• fix: Settings → User Pref → "Key Bright" now applies the new keypad_brightness ratio immediately. The menu used the generic config_option path in text_menu.py, which only wrote to config and never signaled the main loop, so the new ratio didn't take effect until something else (e.g. ALT_+/ALT_-) re-triggered main.set_brightness. Added an apply_brightness post_callback that puts "set_brightness" on the ui_queue; the existing handler in main.py already re-reads keypad_brightness and updates the keypad PWM.
• refactor: Drop the dead _config_options hint-menu dict from UIStatus and the ten unreferenced callbacks below it (update_software, set_key_brightness, set_sleep_timeout, set_hint_timeout, set_screen_off_timeout, mount_switch, side_switch, wifi_switch, shutdown, restart) plus the active() method and version_txt attr that only existed to feed the dead dict. Nothing iterates _config_options anywhere in the codebase, and the duplicated update_software shadowed the live implementation in ui/software.py. Preserved the wifi_status.txt read that seeds status_dict["WIFI"]. Net: −179 / +3 in ui/status.py.

Test plan

• In Settings → User Pref → Key Bright, pick a different ratio (e.g. +3 then -2) and confirm the keypad LEDs change immediately, without needing to also touch display brightness.
• Visit the STATUS screen and confirm it still renders all fields (LAST SLV, RA/DEC, AZ/ALT, WIFI, IP, SSID, IMU, GPS, times, CPU TMP) and that up/down still scroll long content.
• Confirm WiFi indicator shows correctly on first entry to STATUS after boot in both AP and Client modes.

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