Connect backend and frontend to signalR

[andchiind]

Closes #1020 #1063

This PR connects the frontend and backend to SignalR, and then replaces polling for missionRuns and failed missions for the mission queue and failed missions banner.

It is important to note that in order to use signalR in a react context, that context provider must be nested within the signalR provider in flotillasite.tsx

[andchiind]

Currently we have one event that is sent if a mission run is updated in any way. Since this means that an update to a step also implies an update due to a task update, we could potentially create more fine tuned events to avoid unnecessary events in the frontend. So if you are only interested in the status of a mission changing then you could subscribe just to that and ignore step and task updates, for example.

[andchiind]

All frontend polling has been removed except the call to get mission runs within the history page filter. This one could be removed by having the GET request only be made when a "mission run updated/created" event is received which would not be filtered away, but since "mission run updated" is called each time a task is completed, this may create be a small improvement overall, for the price of more complicated code. It may still be worthwhile doing at some point though, especially as it would be satisfying to remove the last reference to "refreshInterval".

[github-actions]

🔔 Migrations changes detected 🔔
📣 Remember to comment "/UpdateDatabase" after review approval for migrations to take effect!

[aeshub]

LGTM

[andchiind]

/UpdateDatabase

[github-actions]

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