Light Sensitive One Pulse Activated Switch
When the circuit is powered up, even if the LDR is dark and the transistors are cut off, there is still a current path through RL1 and then through RL2.  When RL2 turns on, its normally open contacts close, which shorts out the RL2 coil.  This causes the NO contacts to open again, and the cycle repeats forever.  This is why RL2 is buzzing.

Are there any extra contacts on RL1?  If so, you can use some NO contacts from the T1 collector to ground, with the NC pushbutton in series.  Eliminate RL2.  Once the relay is activated, the NO contacts will keep it activated until the button is pushed.