DFTE docs, single root library.json, optional DFTE logging bridge

- Document fork/DFTE in README; WiFiManager template setup API forwards to server
- Remove nested lib/WiFiManager/library.json; rely on root library.json only
- Delete legacy extras/ tooling; point HTML help link at this fork
- Add WiFiManagerDfteLogger and WM_DFTE_LOGGING integration in WiFiManagerServer
- Pin ESP8266 Arduino core (postmortem jump fix) in platformio.ini for tests

platformio.ini

@@ -5,11 +5,14 @@
 platform = espressif8266
 board = d1_mini
 framework = arduino
+; Postmortem jump relocation fix for large binaries (see ESP8266-LINKER-WORKAROUND.md in arduino-home-assistant)
+platform_packages =
+    platformio/framework-arduinoespressif8266 @ https://github.com/esp8266/Arduino.git#521ae60a89e64bb0d1eb7a0b7addf620ced5cad3
 monitor_speed = 115200
 test_framework = unity
 test_build_src = no
 lib_deps = 
-    ESP32Async/ESPAsyncWebServer@3.9.1
+    ESP32Async/ESPAsyncWebServer@^3.9.1
     symlink://../DFTE
 
 [env:esp32]
@@ -24,6 +27,12 @@ build_unflags =
 build_flags = 
     -std=gnu++14
 lib_deps = 
-    ESP32Async/ESPAsyncWebServer@3.9.1
+    ESP32Async/ESPAsyncWebServer@^3.9.1
     symlink://../DFTE
 
+; Optional: compile tests with DFTE logs bridged into DEBUG_WM (see README)
+[env:esp8266_dfte_log]
+extends = env:esp8266
+build_flags =
+    -DWM_DFTE_LOGGING
+