chore(windows): add Windows batch script for one-click startup

Add a Windows batch script to launch both backend and frontend servers with a single click.

This script:
- Starts the Python backend server in a new window
- Starts the Vue.js frontend server in another window
- Includes proper window titles and logging
- Automatically closes the launcher window after 10 seconds

start-win.bat

@@ -0,0 +1,27 @@
+@echo off
+TITLE One-Click Starter for social-auto-upload
+
+ECHO ==================================================
+ECHO  Starting social-auto-upload Servers...
+ECHO ==================================================
+ECHO.
+
+ECHO [1/2] Starting Python Backend Server in a new window...
+REM The START command launches a new process.
+REM The first quoted string "SAU Backend" is the title of the new window.
+REM cmd /k runs the command and keeps the window open to show logs.
+START "SAU Backend" cmd /k "python sau_backend.py"
+
+ECHO [2/2] Starting Vue.js Frontend Server in another new window...
+START "SAU Frontend" cmd /k "cd sau_frontend && npm run dev -- --host 0.0.0.0"
+
+ECHO.
+ECHO ==================================================
+ECHO  Done.
+ECHO  Two new windows have been opened for the backend
+ECHO  and frontend servers. You can monitor logs there.
+ECHO ==================================================
+ECHO.
+
+ECHO This window will close in 10 seconds...
+timeout /t 10 /nobreak > nul