fix(voice): allow WASM compilation in CSP for Silero VAD

Add 'wasm-unsafe-eval' to script-src and blob: to worker-src in
Content-Security-Policy header. Required by onnxruntime-web to compile
the Silero VAD ONNX model. Also surface VAD init errors as a toast
instead of silent console log.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/components/ChatInputBar.vue

@@ -153,10 +153,11 @@ const vad = useVad({
     void stopRecording(false)
   },
   onNoSpeech: () => {
-    // User manually stopped without VAD detecting speech. Toast it; the
-    // stopRecording path below will skip Whisper based on vadSawSpeech.
     useToastStore().show('No speech detected', 'warning')
   },
+  onVadError: (msg) => {
+    useToastStore().show(`VAD failed: ${msg}`, 'error')
+  },
 })
 
 // Live mic halo. A solid red disc sits behind the mic button and scales