feat: Add Windows build and run automation scripts (#8861)

* 🔧 (build_and_run.bat): Add a Windows batch script to build frontend, copy build files to backend, and run Langflow
🔧 (build_and_run.ps1): Add a Windows PowerShell script to build frontend, copy build files to backend, and run Langflow

* 📝 scripts/windows/build_and_run.bat: improve script messages for better clarity and consistency
📝 scripts/windows/build_and_run.ps1: update script steps numbering and messages for consistency and clarity

* 📝 (build_and_run.bat): Add attention message to wait for uvicorn to run before opening the browser
📝 (build_and_run.ps1): Add attention message to wait for uvicorn to run before opening the browser

scripts/windows/build_and_run.bat

@@ -0,0 +1,84 @@
+@echo off
+echo Starting Langflow build and run process...
+
+echo.
+echo Step 1: Installing frontend dependencies...
+cd ..\..\src\frontend
+if errorlevel 1 (
+    echo Error: Could not navigate to src\frontend directory
+    pause
+    exit /b 1
+)
+
+echo Running npm install...
+call npm install
+if errorlevel 1 (
+    echo Error: npm install failed
+    pause
+    exit /b 1
+)
+
+echo.
+echo Step 2: Building frontend...
+echo Running npm run build...
+call npm run build
+if errorlevel 1 (
+    echo Error: npm run build failed
+    pause
+    exit /b 1
+)
+
+echo.
+echo Step 3: Copying build files to backend...
+cd ..\..
+
+REM Check if build directory exists
+if not exist "src\frontend\build" (
+    if not exist "src\frontend\dist" (
+        echo Error: Neither build nor dist directory found in src\frontend
+        pause
+        exit /b 1
+    )
+    set BUILD_DIR=src\frontend\dist
+) else (
+    set BUILD_DIR=src\frontend\build
+)
+
+echo Copying from %BUILD_DIR% to src\backend\base\langflow\frontend\
+REM Create target directory if it doesn't exist
+if not exist "src\backend\base\langflow\frontend" (
+    mkdir "src\backend\base\langflow\frontend"
+)
+
+REM Remove existing files in target directory (FORCES CLEAN REPLACEMENT)
+echo Removing existing files from target directory...
+if exist "src\backend\base\langflow\frontend\*" (
+    del /q /s "src\backend\base\langflow\frontend\*"
+    for /d %%d in ("src\backend\base\langflow\frontend\*") do rmdir /s /q "%%d"
+)
+
+REM Copy all files from build directory
+xcopy "%BUILD_DIR%\*" "src\backend\base\langflow\frontend\" /e /i /y
+if errorlevel 1 (
+    echo Error: Failed to copy build files
+    pause
+    exit /b 1
+)
+
+echo Build files copied successfully!
+
+echo.
+echo Step 4: Running Langflow...
+echo.
+echo Attention: Wait until uvicorn is running before opening the browser
+echo.
+uv run langflow run
+if errorlevel 1 (
+    echo Error: Failed to run langflow
+    pause
+    exit /b 1
+)
+
+echo.
+echo Langflow build and run process completed!
+pause