You need the sqlcompare.exe, which is SQL Compare Pro's command line. The steps you need are:
1) create an svn working folder
2) run sqlcompare.exe with the following switches
/db1:yourdb /s1:yourserver /scripts2:yourworkingfolder /sync
3) run an svn commit
Use an Agent Job, Windows Scheduler or any other tool that can trigger a batch file periodically. If you plan to install this on a server rather than your desktop, you'll need an Automation License to activate the command line.