Have you been to the Adafruit website?
https://www.adafruit.com
They have all the things you need for a project like this. Search for "Arduino Uno Bluetooth". That would be a good platform for your project. The Uno doesn't have Bt built in so you need it added. I work with the ESP32, which has integrated wifi and Bt. Also quite a bit more powerful then the Uno. But your project doesn't need lot of power and the Uno is widely used and community supported. The Arduino IDE is a very simple dev environment but perfect for your application.
You should be able to find an Android app that's generic app for testing.
https://play.google.com/store/apps/d...uit.le.connect
https://maker.pro/arduino/tutorial/b...tphone-arduino
You can search relays on Adafruit and choose one that's suitable for driving the solenoids. The processor uses digital IO to turn them on/off.
Also Youtube is a valuable source of info....
https://www.youtube.com/results?sear...ooth+projects+