Suppress notifications wave upon big sync or restore

[rabble]

When a user restores their feeds / upgrades / reinstalls the app or even reconnects after a long time, the app sends MANY MANY notifications.

We need to rate limit those notifications so that we don't overwhelm the user.

I'm not sure what the right number is but we need a rate limiting system, some value for it, say stop sending notifications after 5, until the user checks the notifications tab or reopens the app. Something, once we have a rate limiting system we can adjust.