Complete Phase 12 dual-stack networking

Add IPv6-aware Wi-Fi state, HTTPS/SSH listeners, mDNS service
reconciliation, and browser Wi-Fi administration.

Include a guarded build-local fix for mDNS 1.12.0 membership handling,
focused regression suites, and Phase 12 acceptance documentation.

cmake/mdns_membership.cmake

@@ -0,0 +1,44 @@
+# Only the lwIP backend needs this fix. Keep the managed component immutable.
+function(project_mdns_membership_overlay)
+    if(CONFIG_MDNS_NETWORKING_SOCKET)
+        return()
+    endif()
+    idf_component_get_property(mdns_dir espressif__mdns COMPONENT_DIR)
+    idf_component_get_property(mdns_lib espressif__mdns COMPONENT_LIB)
+    idf_component_get_property(mdns_version espressif__mdns COMPONENT_VERSION)
+    if(NOT mdns_version STREQUAL "1.12.0")
+        message(FATAL_ERROR "mDNS membership overlay requires component version 1.12.0; review upstream")
+    endif()
+    idf_build_get_property(python PYTHON)
+    set(helper "${CMAKE_CURRENT_LIST_DIR}/mdns_membership.py")
+    set(original "${mdns_dir}/mdns_networking_lwip.c")
+    set(overlay "${CMAKE_BINARY_DIR}/mdns_membership/mdns_networking_lwip.c")
+    set_property(DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS
+        "${helper}" "${original}" "${mdns_dir}/idf_component.yml" "${overlay}")
+    execute_process(COMMAND "${python}" "${helper}" "${mdns_dir}" "${overlay}"
+        RESULT_VARIABLE result OUTPUT_VARIABLE output ERROR_VARIABLE error)
+    if(NOT result EQUAL 0)
+        message(FATAL_ERROR "mDNS membership overlay failed: ${output}${error}")
+    endif()
+
+    get_target_property(sources ${mdns_lib} SOURCES)
+    get_target_property(source_dir ${mdns_lib} SOURCE_DIR)
+    set(replaced 0)
+    set(updated_sources)
+    foreach(source IN LISTS sources)
+        get_filename_component(absolute "${source}" ABSOLUTE BASE_DIR "${source_dir}")
+        if(absolute STREQUAL original)
+            list(APPEND updated_sources "${overlay}")
+            math(EXPR replaced "${replaced} + 1")
+        else()
+            list(APPEND updated_sources "${source}")
+        endif()
+    endforeach()
+    if(NOT replaced EQUAL 1)
+        message(FATAL_ERROR "Expected exactly one mDNS lwIP target source, found ${replaced}; review upstream CMake")
+    endif()
+    set_property(TARGET ${mdns_lib} PROPERTY SOURCES "${updated_sources}")
+    message(STATUS "mDNS 1.12.0: using guarded build-local multicast membership fix")
+endfunction()
+
+project_mdns_membership_overlay()