When driving around 45 MPH a front-end vibration starts?

There are several parts that can cause vibration at 45 MPH. Loose steering and suspension parts can cause this. Problems with the front tires or out of balanced tires can cause vibration. Bent wheels can cause vibration also.
Warped front brake rotors can cause this too but usually only presents when the brake pedal is applied when driving usually at higher speeds. You'll also feel it in the steering wheel when braking but not if rear brake rotors are warped.
You can try inspecting the tires for any damage or unusual wear. You could rotate the tires front to back to see if that changes anything and if it does then the problem is with the tires or wheels (rims).
While you have the vehicle off the ground check for loose steering or suspension parts.

I would start with the brake rotors first based off your explanation.

Let us know what you find.

When you have the tires off the ground you can check and inspect the tie rod ends, ball joints and control arm bushings.
Check for any movement in these parts. You shouldn't have any play in the inner or outer title rod ends. No play in the ball joints either. Control arm bushings shouldn't be split, broken or separated.

Here are some YouTube videos going over how to check these components.
For the control arm bushing I would raise the vehicle off the ground and using a pry bar to flex the control arm bushings to look for play, large splitting or separation.

https://youtu.be/6M2D_XtuXZQ?si=7-qKwCcGeFtNwy5s

https://youtu.be/brI2feYiEi8?si=hZcI-850DOYr9kh8