docs: add Windows HTML build script

doc/build-html.bat

@@ -0,0 +1,35 @@
+@echo off
+setlocal EnableExtensions
+
+set "SCRIPT_DIR=%~dp0"
+set "SOURCE_FILE=%SCRIPT_DIR%index.html"
+set "BUILD_DIR=%SCRIPT_DIR%build"
+set "OUTPUT_FILE=%BUILD_DIR%\index.html"
+
+if not exist "%SOURCE_FILE%" (
+    echo [ERROR] Source file not found:
+    echo         %SOURCE_FILE%
+    exit /b 1
+)
+
+if not exist "%BUILD_DIR%" (
+    mkdir "%BUILD_DIR%"
+    if errorlevel 1 (
+        echo [ERROR] Cannot create build directory:
+        echo         %BUILD_DIR%
+        exit /b 2
+    )
+)
+
+copy /Y "%SOURCE_FILE%" "%OUTPUT_FILE%" >nul
+if errorlevel 1 (
+    echo [ERROR] Cannot build HTML.
+    exit /b 3
+)
+
+for %%F in ("%OUTPUT_FILE%") do set "OUTPUT_SIZE=%%~zF"
+echo [OK] HTML documentation rebuilt:
+echo      %OUTPUT_FILE%
+echo      %OUTPUT_SIZE% bytes
+
+exit /b 0