What does “from your end” mean?

In this context, the word 'end' is referring to one (of two) members in the communication: you and the Russians. The question is asking whether the Russians sought a relationship with you, or if you sought a relationship with the Russians.

It might be helpful to try replacing the word 'end' with 'perspective':

Or did you seek it from your perspective?

"From your end" means "on your part"

In English when someone says "from your end" they mean, from your side of the communication, referring to you communicating with the Russians in your specific example.

Before cell phones, there were land line phones and older communications that were not wireless but required wires to connect two people in conversations. Each wire "end" was at one person's location.

So if you were to be on a land-line phone conversation with the Russians there would be two ends/sides to this connection, your end and their end of the communication.