Add wake word to xmini-c3 (#730)

* esp-hi: MCP protocol is not ready yet

* Add wake word to xmini-c3

main/audio_processing/no_wake_word.cc

@@ -0,0 +1,45 @@
+#include "no_wake_word.h"
+#include <esp_log.h>
+
+#define TAG "NoWakeWord"
+
+void NoWakeWord::Initialize(AudioCodec* codec) {
+    codec_ = codec;
+}
+
+void NoWakeWord::Feed(const std::vector<int16_t>& data) {
+    // Do nothing - no wake word processing
+}
+
+void NoWakeWord::OnWakeWordDetected(std::function<void(const std::string& wake_word)> callback) {
+    // Do nothing - no wake word processing
+}
+
+void NoWakeWord::StartDetection() {
+    // Do nothing - no wake word processing
+}
+
+void NoWakeWord::StopDetection() {
+    // Do nothing - no wake word processing
+}
+
+bool NoWakeWord::IsDetectionRunning() {
+    return false;  // No wake word processing
+}
+
+size_t NoWakeWord::GetFeedSize() {
+    return 0;  // No specific feed size requirement
+}
+
+void NoWakeWord::EncodeWakeWordData() {
+    // Do nothing - no encoding needed
+}
+
+bool NoWakeWord::GetWakeWordOpus(std::vector<uint8_t>& opus) {
+    opus.clear();
+    return false;  // No opus data available
+}
+
+const std::string& NoWakeWord::GetLastDetectedWakeWord() const {
+    return "";  // No wake word detected
+}