Is your repository on the same server where you installed Trac? If so, you can access the repository directly instead of going through http. For example, if your repository was created in /var/repos/trac, adding the following into your trac.ini should work:
[trac]
repository_dir = /var/repos/trac
If your repository is on a different server, I highly recommend either installing Trac on the repository's server or creating a mirror repository on the Trac server. Besides making the Trac configuration easier, it results in a much faster Trac server by avoiding the need to fetch repository information over the network. Create the mirror repository but don't start any kind of Subversion server; Trac can still access it directly via the filesystem, and you don't have to worry about anyone but Trac accessing it. You can set up a simple script that runs svnsync synchronize at regular intervals (mine is set to 5 minutes) to keep your mirror up to date.
On another note, using repository_dir in trac.ini is no longer the preferred way to set up a repository. It's usually easier to use the "Repositories" panel of Trac's admin panel (see the official documentation for more details). If you go that route, make sure to delete the existing repository_dir entry from your trac.ini first.
