feat: Add .env file support to Windows build scripts (#9214)

* 🔧 (build_and_run.bat): add support for loading environment variables from .env file
🔧 (build_and_run.ps1): add support for loading environment variables from .env file

* 🐛 (build_and_run.bat): fix path to .env file to correctly load environment variables
🐛 (build_and_run.ps1): fix path to .env file to correctly load environment variables

* 🔧 (build_and_run.bat): set env file parameter if .env file exists to pass to langflow run
🔧 (build_and_run.ps1): set env file parameter if .env file exists to pass to langflow run

* 📝 (build_and_run.bat): improve script to dynamically find and set .env file path for Langflow run
📝 (build_and_run.ps1): enhance script to dynamically locate and set .env file path for Langflow run

* Update scripts/windows/build_and_run.bat

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

* 🔧 (build_and_run.ps1): refactor script to use a boolean flag 'useEnvFile' instead of a string variable 'envFileParam' to improve readability and maintainability
🔧 (build_and_run.ps1): update uvicorn command to use '--env-file' flag directly instead of building the command with a string variable

---------

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

scripts/windows/build_and_run.bat

@@ -1,6 +1,19 @@
 @echo off
 echo Starting Langflow build and run process...
 
+REM Check if .env file exists and set env file parameter
+set "ENV_FILE_PARAM="
+REM Get the script directory and resolve project root
+for %%I in ("%~dp0..\..") do set "PROJECT_ROOT=%%~fI"
+set "ENV_PATH=%PROJECT_ROOT%\.env"
+if exist "%ENV_PATH%" (
+    echo Found .env file at: %ENV_PATH%
+    set "ENV_FILE_PARAM=--env-file \"%ENV_PATH%\""
+) else (
+    echo .env file not found at: %ENV_PATH%
+    echo Langflow will use default configuration
+)
+
 echo.
 echo Step 1: Installing frontend dependencies...
 cd ..\..\src\frontend
@@ -72,7 +85,11 @@ echo Step 4: Running Langflow...
 echo.
 echo Attention: Wait until uvicorn is running before opening the browser
 echo.
+if defined ENV_FILE_PARAM (
+    uv run langflow run %ENV_FILE_PARAM%
+) else (
     uv run langflow run
+)
 if errorlevel 1 (
     echo Error: Failed to run langflow
     pause

scripts/windows/build_and_run.ps1

@@ -2,6 +2,19 @@
 
 Write-Host "Starting Langflow build and run process..." -ForegroundColor Green
 
+# Check if .env file exists and set env file parameter
+$scriptDir = Split-Path -Parent $MyInvocation.MyCommand.Definition
+$projectRoot = Resolve-Path (Join-Path $scriptDir "..\..")
+$envPath = Join-Path $projectRoot ".env"
+$useEnvFile = $false
+if (Test-Path $envPath) {
+    Write-Host "Found .env file at: $envPath" -ForegroundColor Cyan
+    $useEnvFile = $true
+} else {
+    Write-Host ".env file not found at: $envPath" -ForegroundColor Yellow
+    Write-Host "Langflow will use default configuration" -ForegroundColor Yellow
+}
+
 # Step 1: Install frontend dependencies
 Write-Host "`nStep 1: Installing frontend dependencies..." -ForegroundColor Yellow
 try {
@@ -73,7 +86,11 @@ try {
 Write-Host "`nStep 4: Running Langflow..." -ForegroundColor Yellow
 Write-Host "`nAttention: Wait until uvicorn is running before opening the browser" -ForegroundColor Red
 try {
-    uv run langflow run
+    if ($useEnvFile) {
+        & uv run langflow run --env-file $envPath
+    } else {
+        & uv run langflow run
+    }
 } catch {
     Write-Host "Error running langflow: $_" -ForegroundColor Red
     Read-Host "Press Enter to exit"