fix: support configurable bind host for HTTP API and fix Windows sherpa-onnx PATH

- fix(#547): HTTP API server now supports configurable bind host (default 127.0.0.1)
  Docker/N8N users can set host to 0.0.0.0 in settings to allow container access.
  Adds httpApiHost config key, UI input in settings, and passes host through
  IPC chain (preload -> main -> httpService).

- fix(#546): Add Windows PATH injection for sherpa-onnx native module
  buildTranscribeWorkerEnv() now adds the sherpa-onnx-win-x64 directory to
  PATH on Windows, fixing 'Could not find sherpa-onnx-node' errors caused
  by missing DLL search path in forked worker processes.

src/types/electron.d.ts

@@ -838,7 +838,7 @@ export interface ElectronAPI {
     getLogs: () => Promise<string[]>
   }
   http: {
-    start: (port?: number) => Promise<{ success: boolean; port?: number; error?: string }>
+    start: (port?: number, host?: string) => Promise<{ success: boolean; port?: number; error?: string }>
     stop: () => Promise<{ success: boolean }>
     status: () => Promise<{ running: boolean; port: number; mediaExportPath: string }>
   }