Fix format specifier for SSID debug log in WifiConnector::connect

[qwerty1979bg]

What

One-character fix: %d → %s in the Serial.printf call that logs the
configured SSID before attempting to connect to it.

Why

wifiSSID.c_str() is a const char*; %d expects an int. The mismatch
meant the log never showed the actual SSID — just the pointer value
interpreted as a decimal integer. Doesn't crash on this target (pointer and
int are both 4 bytes on ESP32), but the diagnostic was silently useless.

This is how it looked in the logs:
Attempt connect to configured ssid: 1070229276
(While the SSID is something else and not a literal 1070229276)

Fixes #384

Test plan

• Flash to a device with a saved SSID, confirm serial log now prints
  the real SSID instead of a numeric value

Note: drafted with AI assistance, verified manually