Register endpoints before stack startup

[puddly]

579 moved endpoint registration after network startup, causing it to actually fail on real devices.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (b22db97) 99.83% compared to head (5e535e3) 99.83%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## dev #588 +/- ## ======================================= Coverage 99.83% 99.83% ======================================= Files 68 68 Lines 4874 4882 +8 ======================================= + Hits 4866 4874 +8 Misses 8 8 ``` | [Files](https://app.codecov.io/gh/zigpy/bellows/pull/588?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=zigpy) | Coverage Δ | | |---|---|---| | [bellows/exception.py](https://app.codecov.io/gh/zigpy/bellows/pull/588?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=zigpy#diff-YmVsbG93cy9leGNlcHRpb24ucHk=) | `100.00% <100.00%> (ø)` | | | [bellows/zigbee/application.py](https://app.codecov.io/gh/zigpy/bellows/pull/588?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=zigpy#diff-YmVsbG93cy96aWdiZWUvYXBwbGljYXRpb24ucHk=) | `100.00% <100.00%> (ø)` | |

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