[wifi] Add optional multi_ap mode to select strongest AP by RSSI

[deltecent]

Summary

Fixes #1575.

ESP-IDF's default WIFI_FAST_SCAN associates to the first AP that answers for the configured SSID, ignoring signal strength. In a meshed / multi-AP SSID (extenders/repeaters, mixed 2.4/5 GHz), a stationary FujiNet can latch onto a weak/distant AP and stay there — flaky throughput and periodic disconnects even when a much stronger same-SSID AP is available.

Approach: opt-in via config, fast scan stays the default

This adds a multi_ap option to the existing [WiFi] section of fnconfig.ini (default 0). Behavior is unchanged unless it's turned on.

[WiFi]
...
multi_ap=1

When enabled, WiFiManager::connect() and test_connect() set an all-channel, signal-sorted scan before esp_wifi_set_config:

if (Config.get_wifi_multi_ap())
{
    wifi_config.sta.scan_method = WIFI_ALL_CHANNEL_SCAN;
    wifi_config.sta.sort_method = WIFI_CONNECT_AP_BY_SIGNAL;
}

so the strongest same-SSID AP is chosen at connect time. No minimum-RSSI threshold is set, so a lone weak AP stays usable.

It also logs bssid / channel / rssi on WIFI_EVENT_STA_CONNECTED (unconditional — useful in both scan modes) so the selected AP is visible in the debug output.

Why opt-in

WIFI_ALL_CHANNEL_SCAN scans every channel before associating, so connection setup is somewhat slower than fast scan. Rather than change the default connect path for everyone, this leaves fast scan as the default and lets users in meshed/multi-AP environments opt in.

Changes

• lib/hardware/fnWiFi.cpp — gate the all-channel/signal-sorted scan on Config.get_wifi_multi_ap() in connect() and test_connect(); log AP bssid/channel/rssi on connect. (ESP-only; the PC build uses fnDummyWiFi.)
• lib/config/fnConfig.h, fnc_wifi.cpp, fnc_save.cpp — wifi_info.multi_ap field, get/store_wifi_multi_ap(), and parse/save in the existing [WiFi] section.

Testing

• FujiNet-PC RS232 build + ctest suite green (config plumbing compiles; fnc_wifi/fnc_save exercised by the build).
• ESP behavioral verification of the scan modes is still worth a real-hardware check in a multi-AP setup.

🤖 Generated with Claude Code

https://claude.ai/code/session_01GXyRJPxQQxGYBUHJRJG6JY