fix: startup deadlock

[mvarendorff2]

This PR fixes a deadlock in startup that occurs when placing .AddEventSourcing() before .AddPostgresEventSourcingRepository(). This caused the the SideEffectDispatcher to wait for Upcasting to be finished while the Upcaster as HostedService waits for the SideEffectDispatcher StartAsync to finish.

[codecov]

Codecov Report

Attention: Patch coverage is 58.33333% with 5 lines in your changes missing coverage. Please review.

Project coverage is 66.67%. Comparing base (949242e) to head (a7c3630).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
...rc/Fluss.PostgreSQL/ServiceCollectionExtensions.cs	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #50      +/-   ##
==========================================
+ Coverage   66.62%   66.67%   +0.05%     
==========================================
  Files          75       75              
  Lines        2873     2878       +5     
  Branches      303      303              
==========================================
+ Hits         1914     1919       +5     
- Misses        906      907       +1     
+ Partials       53       52       -1     

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