Fix hosted service registration ambiguity in channel runtime

[eanzhao]

Summary

• replace the factory-based IHostedService registration for the Lark inbox runtime
• add a thin hosted-service adapter that delegates to the shared runtime singleton
• keep ILarkConversationInbox and hosted startup bound to the same runtime instance

Problem

.NET 10 rejects TryAddEnumerable(ServiceDescriptor.Singleton<IHostedService>(factory)) for IHostedService because the implementation type is indistinguishable from other hosted-service registrations. AddChannelRuntime(...) hit that path during startup and the host failed before serving traffic.

Solution

• keep LarkConversationInboxRuntime as the concrete singleton
• keep ILarkConversationInbox resolving to that singleton
• introduce LarkConversationInboxHostedService as a small adapter implementing IHostedService
• register the adapter via TryAddEnumerable(ServiceDescriptor.Singleton<IHostedService, LarkConversationInboxHostedService>())

Verification

• dotnet build src/Aevatar.Mainnet.Host.Api/Aevatar.Mainnet.Host.Api.csproj --nologo

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.74%. Comparing base (1d749ac) to head (f85fc3c).
⚠️ Report is 2 commits behind head on dev.

@@           Coverage Diff           @@
##              dev     #314   +/-   ##
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  Coverage   69.73%   69.74%           
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  Files        1139     1139           
  Lines       81170    81170           
  Branches    10619    10619           
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+ Hits        56605    56612    +7     
+ Misses      20469    20463    -6     
+ Partials     4096     4095    -1     

Flag	Coverage Δ
ci	69.74% <ø> (+<0.01%)	⬆️

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