feat(speech): add prompt voice input (#249)

## Summary
- add server-backed speech capabilities and transcription endpoints plus
UI settings for speech configuration
- add push-to-talk prompt voice input with microphone controls,
transcription insertion, and browser capability gating
- keep prompt controls aligned by restoring right-side nav placement and
moving the mic beside the expand control

packages/ui/src/App.tsx

@@ -68,6 +68,7 @@ const App: Component = () => {
     toggleAutoCleanupBlankSessions,
     toggleUsageMetrics,
     togglePromptSubmitOnEnter,
+    toggleShowPromptVoiceInput,
     setDiffViewMode,
     setToolOutputExpansion,
     setDiagnosticsExpansion,
@@ -353,6 +354,7 @@ const App: Component = () => {
     toggleShowTimelineTools,
     toggleUsageMetrics,
     togglePromptSubmitOnEnter,
+    toggleShowPromptVoiceInput,
     setDiffViewMode,
     setToolOutputExpansion,
     setDiagnosticsExpansion,