Add install.bat Windows installer and update .gitignore

.gitignore

@@ -4,3 +4,6 @@ __pycache__/
 temp_project.json
 verify_flowchart.py
 generate_screenshot.py
+.venv/
+run_desktop.bat
+run_web.bat

install.bat

@@ -0,0 +1,58 @@
+@echo off
+echo ==================================================
+echo B^&W Flowchart Sketcher - Installer
+echo ==================================================
+echo.
+
+:: 1. Check Python
+python --version >nul 2>&1
+if %errorlevel% neq 0 (
+    echo [ERROR] Python is not installed or not in system PATH.
+    echo Please install Python (3.8+) and check "Add Python to PATH" during setup.
+    pause
+    exit /b 1
+)
+
+:: 2. Create Virtual Environment
+echo [1/3] Creating virtual environment (.venv)...
+python -m venv .venv
+if %errorlevel% neq 0 (
+    echo [ERROR] Failed to create virtual environment.
+    pause
+    exit /b 1
+)
+
+:: 3. Install Dependencies
+echo [2/3] Installing dependencies inside virtual environment...
+call .venv\Scripts\activate.bat
+python -m pip install --upgrade pip
+python -m pip install -r requirements.txt
+if %errorlevel% neq 0 (
+    echo [ERROR] Failed to install dependencies.
+    pause
+    exit /b 1
+)
+
+:: 4. Create Launcher Scripts
+echo [3/3] Creating quick launch shortcuts...
+
+echo @echo off > run_desktop.bat
+echo echo Starting B^&W Flowchart Sketcher (Desktop App)... >> run_desktop.bat
+echo call .venv\Scripts\activate.bat >> run_desktop.bat
+echo python flowchart_app.py >> run_desktop.bat
+
+echo @echo off > run_web.bat
+echo echo Starting B^&W Flowchart Sketcher (Web App)... >> run_web.bat
+echo call .venv\Scripts\activate.bat >> run_web.bat
+echo streamlit run app.py >> run_web.bat
+
+echo.
+echo ==================================================
+echo [SUCCESS] Installation Complete!
+echo ==================================================
+echo.
+echo You can now use the following launcher scripts:
+echo   - Double-click 'run_desktop.bat' to launch the Desktop application.
+echo   - Double-click 'run_web.bat' to launch the Streamlit Web application.
+echo.
+pause