feat: mic level bar in recording overlay

- InputBar: QProgressBar with gradient (green→yellow→red) in recording overlay
- updateRecordingUI: computes dB from peakLevel, updates bar every 100ms
- showRecordOverlay: resets bar to 0 on new recording

tools/chatgui/src/inputbar.cpp

@@ -16,6 +16,8 @@
 #include <QLabel>
 #include <QResizeEvent>
 #include <QDir>
+#include <QProgressBar>
+#include <cmath>
 
 static QPushButton *makeIconBtn(const QString &text, const QString &tooltip, QWidget *parent) {
     auto *btn = new QPushButton(text, parent);
@@ -115,6 +117,18 @@ InputBar::InputBar(EmojiPanel *emojiPanel, AudioRecorder *recorder, QWidget *par
     m_recordLabel = new QLabel(m_recordOverlay);
     m_recordLabel->setStyleSheet("color: white; font-size: 14px; font-weight: bold; background: transparent;");
     roLayout->addWidget(m_recordLabel);
+
+    m_levelBar = new QProgressBar(m_recordOverlay);
+    m_levelBar->setRange(0, 100);
+    m_levelBar->setValue(0);
+    m_levelBar->setTextVisible(false);
+    m_levelBar->setFixedSize(80, 14);
+    m_levelBar->setStyleSheet(
+        "QProgressBar { border: 1px solid rgba(255,255,255,0.2); border-radius: 3px; background: rgba(0,0,0,0.3); }"
+        "QProgressBar::chunk { background: qlineargradient(x1:0, y1:0, x2:1, y2:0,"
+        " stop:0 #27ae60, stop:0.6 #f1c40f, stop:1 #e74c3c); border-radius: 2px; }");
+    roLayout->addWidget(m_levelBar);
+
     roLayout->addStretch();
     m_cancelRecBtn = new QPushButton(QString::fromUtf8("\xE2\x9C\x95"), m_recordOverlay);
     m_cancelRecBtn->setFixedSize(24, 24);
@@ -261,6 +275,7 @@ void InputBar::showRecordOverlay() {
         m_recordOverlay->show();
         m_recordOverlay->raise();
         m_recordLabel->setText(QString::fromUtf8("\xF0\x9F\x94\xB4 Recording 0:00"));
+        if (m_levelBar) m_levelBar->setValue(0);
     }
 }
 
@@ -274,4 +289,11 @@ void InputBar::updateRecordingUI(int ms) {
         m_recordLabel->setText(QString::fromUtf8("\xF0\x9F\x94\xB4 Recording %1:%2")
             .arg(secs / 60).arg(secs % 60, 2, 10, QChar('0')));
     }
+    if (m_levelBar && m_recorder) {
+        float peak = m_recorder->peakLevel();
+        float db = peak > 0.0001f ? 20.0f * log10f(peak) : -70.0f;
+        int pct = (int)((db + 70.0f) / 70.0f * 100.0f);
+        if (pct < 0) pct = 0; if (pct > 100) pct = 100;
+        m_levelBar->setValue(pct);
+    }
 }