Typically, the wireless devices are not specified in the network config... instead, the network to which the wireless should attach is defined in the wireless config file.
The br-lan allows you to use ethernet + wireless.
But as I look at it now, the br-lan and the wan are both defined to use eth0. You should remove eth0 from br-lan. If you only have one ethernet port, you don't really need to use br-lan since your device only appears to have a single radio. However, you should still remove the wlan0 device from your network configuration. If you happen to have multiple ethernet ports, you'll probably want eth1 in br-lan and then you can use br-lan for the network device for lan.
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