fix: notifications fixes

[Tanya-atatakai]

There are two issues with notifications:

1. On the first run, a user should stake 20 OLAS. When the agent runs for the first time, we show a modal and a notification. The problem is that the notification shows "undefined" instead of "20" because we get the value from the existing service, which is actually not yet created when we call showNotification.

I changed the logic to get the minimumStakedAmountRequired from the template instead of from the service and removed it from the useReward since it's not used anywhere else. I also updated the NeedsFunds modal so it has the same source of truth.

The error:

After the fix:

2)The "first staking rewards earned" notification is shown for me multiple times in a row until the modal is closed. It happens due to the fact that useEffect has availableRewardsForEpochEth in its dependencies, which is slightly updated with every balance request that happens by interval. I used a ref here to get the first value, so the showNotification is only triggered once.