feat: matrice de routing audio style Dante Controller (Phase 2.5)

- API GET/POST /admin/audio/routing
- Composant AudioRoutingMatrix avec 2 matrices :
  * Inputs vers Groupes (8 inputs x N groupes)
  * Groupes vers Outputs (N groupes x 8 outputs)
- Interface visuelle type grille cliquable
- Intégration noms de canaux personnalisés
- Stockage routing dans config.yaml
- Responsive design avec CSS Grid
- Style cohérent avec interface admin

server/api/admin.js

@@ -578,6 +578,67 @@ router.put('/audio/channels/names', (req, res) => {
   }
 });
 
+/**
+ * GET /admin/audio/routing
+ * Récupère la configuration de routing actuelle
+ * Format: { inputToGroup: { "0": ["production"], "1": ["technique"] }, groupToOutput: { "production": ["0", "1"] } }
+ */
+router.get('/audio/routing', (req, res) => {
+  try {
+    const config = configManager.get();
+    const routing = config.audio?.routing || { inputToGroup: {}, groupToOutput: {}, gains: {} };
+
+    res.json({
+      routing
+    });
+  } catch (error) {
+    console.error('Erreur GET /admin/audio/routing:', error);
+    res.status(500).json({ error: 'Failed to load routing' });
+  }
+});
+
+/**
+ * POST /admin/audio/routing
+ * Sauvegarde la configuration de routing
+ * Body: { inputToGroup: {...}, groupToOutput: {...}, gains: {...} }
+ */
+router.post('/admin/audio/routing', (req, res) => {
+  try {
+    const { inputToGroup, groupToOutput, gains } = req.body;
+
+    const config = configManager.get();
+
+    if (!config.audio.routing) {
+      config.audio.routing = { inputToGroup: {}, groupToOutput: {}, gains: {} };
+    }
+
+    if (inputToGroup !== undefined) {
+      config.audio.routing.inputToGroup = inputToGroup;
+    }
+
+    if (groupToOutput !== undefined) {
+      config.audio.routing.groupToOutput = groupToOutput;
+    }
+
+    if (gains !== undefined) {
+      config.audio.routing.gains = gains;
+    }
+
+    configManager.save(config);
+
+    addLog('info', 'Audio routing updated');
+
+    res.json({
+      message: 'Audio routing updated',
+      routing: config.audio.routing
+    });
+
+  } catch (error) {
+    console.error('Erreur POST /admin/audio/routing:', error);
+    res.status(500).json({ error: 'Failed to update routing' });
+  }
+});
+
 /**
  * POST /admin/audio/device
  * Sélectionne et configure une carte son