Hey everyone I am looking for some advice and suggestions.

I am a volunteer with a community fire brigade and we are looking to improve our Wi-Fi coverage in parts our our fire station. We presently have one router with wi-fi in our office area (stuck in a small comms cabinet), this does not provide any coverage to our truck bay area and the cabinet kills the signal in the office area

We want to improve this by installing an AP in the office area on the ceiling and another in the truck shed using ethernet backhaul to the first AP because we are very limited with ports on the router, we have one cat5 cable strung to the appliance shed and we wish to keep the same SSID throughout. We do not want to use a software or hardware controller so standalone is a must (if we need an app on a phone we can come at this)
Budget is a big constraint, but we can spend a little to get the results we need.

Any help greatly appreciated.