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.

electron/services/config.ts

@@ -54,6 +54,7 @@ interface ConfigSchema {
   messagePushEnabled: boolean
   httpApiEnabled: boolean
   httpApiPort: number
+  httpApiHost: string
   httpApiToken: string
   windowCloseBehavior: 'ask' | 'tray' | 'quit'
   quoteLayout: 'quote-top' | 'quote-bottom'
@@ -125,6 +126,7 @@ export class ConfigService {
       httpApiToken: '',
       httpApiEnabled: false,
       httpApiPort: 5031,
+      httpApiHost: '127.0.0.1',
       messagePushEnabled: false,
       windowCloseBehavior: 'ask',
       quoteLayout: 'quote-top',