feat: ajout dropdowns gain par route dans matrice routing

- Dropdown gain -12dB à +6dB pour chaque route active
- Interface visuelle améliorée (checkbox + gain)
- Gestion gains input->group et group->output
- Sauvegarde gains dans config.yaml
- Design responsive mobile

client/src/components/AudioRoutingMatrix.css

@@ -84,15 +84,25 @@
 
 .matrix-cell {
   background: var(--color-bg);
-  padding: var(--spacing-md);
-  min-height: 40px;
-  min-width: 60px;
-  cursor: pointer;
+  padding: var(--spacing-sm);
+  min-height: 60px;
+  min-width: 80px;
   transition: all 0.2s;
   display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  gap: var(--spacing-xs);
+  position: relative;
+}
+
+.cell-checkbox {
+  width: 100%;
+  min-height: 30px;
+  display: flex;
   align-items: center;
   justify-content: center;
-  position: relative;
+  cursor: pointer;
 }
 
 .matrix-cell:hover {
@@ -114,6 +124,25 @@
   font-weight: bold;
 }
 
+.gain-select {
+  width: 100%;
+  padding: 4px 8px;
+  font-size: 0.75rem;
+  background: rgba(255, 255, 255, 0.9);
+  color: var(--color-text);
+  border: 1px solid rgba(255, 255, 255, 0.3);
+  border-radius: 4px;
+  cursor: pointer;
+  font-weight: 600;
+  text-align: center;
+}
+
+.gain-select:focus {
+  outline: none;
+  border-color: rgba(255, 255, 255, 0.6);
+  box-shadow: 0 0 0 2px rgba(255, 255, 255, 0.2);
+}
+
 @media (max-width: 1024px) {
   .matrix-header-cell,
   .matrix-label-cell {
@@ -123,10 +152,15 @@
   }
 
   .matrix-cell {
-    min-width: 50px;
-    min-height: 35px;
+    min-width: 70px;
+    min-height: 50px;
     padding: var(--spacing-sm);
   }
+
+  .gain-select {
+    font-size: 0.7rem;
+    padding: 3px 6px;
+  }
 }
 
 @media (max-width: 768px) {
@@ -147,11 +181,16 @@
   }
 
   .matrix-cell {
-    min-width: 40px;
-    min-height: 30px;
+    min-width: 65px;
+    min-height: 45px;
   }
 
   .checkmark {
     font-size: 1rem;
   }
+
+  .gain-select {
+    font-size: 0.65rem;
+    padding: 2px 4px;
+  }
 }

client/src/components/AudioRoutingMatrix.jsx

@@ -100,6 +100,39 @@ function AudioRoutingMatrix({ groups, channelNames }) {
     return routing.groupToOutput[groupId]?.includes(outputId) || false;
   };
 
+  const getGainForInputToGroup = (inputId, groupId) => {
+    const key = `in_${inputId}_${groupId}`;
+    return routing.gains?.[key] || 0.0;
+  };
+
+  const getGainForGroupToOutput = (groupId, outputId) => {
+    const key = `${groupId}_out_${outputId}`;
+    return routing.gains?.[key] || 0.0;
+  };
+
+  const setGainForInputToGroup = (inputId, groupId, gainDb) => {
+    setRouting(prev => {
+      const gains = { ...prev.gains };
+      const key = `in_${inputId}_${groupId}`;
+      gains[key] = parseFloat(gainDb);
+      return { ...prev, gains };
+    });
+  };
+
+  const setGainForGroupToOutput = (groupId, outputId, gainDb) => {
+    setRouting(prev => {
+      const gains = { ...prev.gains };
+      const key = `${groupId}_out_${outputId}`;
+      gains[key] = parseFloat(gainDb);
+      return { ...prev, gains };
+    });
+  };
+
+  const formatGain = (gainDb) => {
+    if (gainDb === 0) return '0dB';
+    return gainDb > 0 ? `+${gainDb}dB` : `${gainDb}dB`;
+  };
+
   const getChannelName = (type, id) => {
     const name = channelNames?.[type]?.[id];
     return name || `${type === 'inputs' ? 'Input' : 'Output'} ${id}`;
@@ -169,15 +202,39 @@ function AudioRoutingMatrix({ groups, channelNames }) {
                 {getChannelName('inputs', i)}
               </div>
 
-              {groups.map(group => (
-                <div
-                  key={`${i}-${group.id}`}
-                  className={`matrix-cell ${isInputRoutedToGroup(String(i), group.id) ? 'active' : ''}`}
-                  onClick={() => toggleInputToGroup(String(i), group.id)}
-                >
-                  {isInputRoutedToGroup(String(i), group.id) && <span className="checkmark">✓</span>}
-                </div>
-              ))}
+              {groups.map(group => {
+                const isRouted = isInputRoutedToGroup(String(i), group.id);
+                const gain = getGainForInputToGroup(String(i), group.id);
+
+                return (
+                  <div
+                    key={`${i}-${group.id}`}
+                    className={`matrix-cell ${isRouted ? 'active' : ''}`}
+                  >
+                    <div
+                      className="cell-checkbox"
+                      onClick={() => toggleInputToGroup(String(i), group.id)}
+                    >
+                      {isRouted && <span className="checkmark">✓</span>}
+                    </div>
+                    {isRouted && (
+                      <select
+                        className="gain-select"
+                        value={gain}
+                        onChange={(e) => setGainForInputToGroup(String(i), group.id, e.target.value)}
+                        onClick={(e) => e.stopPropagation()}
+                      >
+                        <option value="-12">-12dB</option>
+                        <option value="-6">-6dB</option>
+                        <option value="-3">-3dB</option>
+                        <option value="0">0dB</option>
+                        <option value="3">+3dB</option>
+                        <option value="6">+6dB</option>
+                      </select>
+                    )}
+                  </div>
+                );
+              })}
             </React.Fragment>
           ))}
         </div>
@@ -204,15 +261,39 @@ function AudioRoutingMatrix({ groups, channelNames }) {
                 {group.name}
               </div>
 
-              {getVisibleOutputChannels().map(i => (
-                <div
-                  key={`${group.id}-${i}`}
-                  className={`matrix-cell ${isGroupRoutedToOutput(group.id, String(i)) ? 'active' : ''}`}
-                  onClick={() => toggleGroupToOutput(group.id, String(i))}
-                >
-                  {isGroupRoutedToOutput(group.id, String(i)) && <span className="checkmark">✓</span>}
-                </div>
-              ))}
+              {getVisibleOutputChannels().map(i => {
+                const isRouted = isGroupRoutedToOutput(group.id, String(i));
+                const gain = getGainForGroupToOutput(group.id, String(i));
+
+                return (
+                  <div
+                    key={`${group.id}-${i}`}
+                    className={`matrix-cell ${isRouted ? 'active' : ''}`}
+                  >
+                    <div
+                      className="cell-checkbox"
+                      onClick={() => toggleGroupToOutput(group.id, String(i))}
+                    >
+                      {isRouted && <span className="checkmark">✓</span>}
+                    </div>
+                    {isRouted && (
+                      <select
+                        className="gain-select"
+                        value={gain}
+                        onChange={(e) => setGainForGroupToOutput(group.id, String(i), e.target.value)}
+                        onClick={(e) => e.stopPropagation()}
+                      >
+                        <option value="-12">-12dB</option>
+                        <option value="-6">-6dB</option>
+                        <option value="-3">-3dB</option>
+                        <option value="0">0dB</option>
+                        <option value="3">+3dB</option>
+                        <option value="6">+6dB</option>
+                      </select>
+                    )}
+                  </div>
+                );
+              })}
             </React.Fragment>
           ))}
         </div>