Refactor runtime host initialization

[Denny09310]

Summary

• introduce IElectronHost, ElectronHost, and ElectronHostEnvironment to encapsulate runtime state and expose it through dependency injection instead of the brittle ElectronNetRuntime static class
• update runtime controllers, bridge components, samples, integration tests, and documentation to consume the new host abstraction and register it from ASP.NET builders
• add configurable options handling plus shared default constants to simplify port handling and remove direct static dependencies

Testing

• dotnet build src/ElectronNET.API/ElectronNET.API.csproj (fails: dotnet command is not available in the execution environment)

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Codex Task