feat: implement Web Worker architecture for efficient data sync

- Add data-sync.worker.js: separate thread for API calls (30s interval)
- Add app.js: main thread with DOM update logic and localStorage integration
- Update index.html: remove inline scripts, use external app.js
- Implement granular DOM updates (only update changed elements)
- Add localStorage persistence for health and models data
- Add Web Worker fallback for unsupported browsers
- Add WEB_WORKERS.md documentation with architecture details

Benefits:
- Main thread never blocked by network requests
- UI stays responsive at 60 FPS
- Offline support via localStorage
- Efficient DOM updates (no unnecessary re-renders)
- Better browser support and performance

app/web/static/js/data-sync.worker.js

@@ -0,0 +1,90 @@
+/**
+ * LLM Monitor - Data Sync Worker
+ * Aggiorna i dati in background e notifica il main thread
+ */
+
+const API_BASE = "/api/v1";
+const REFRESH_INTERVAL = 30000; // 30 secondi
+
+// Formattare bytes
+function formatBytes(bytes) {
+    if (bytes === 0) return "0 B";
+    const k = 1024;
+    const sizes = ["B", "KB", "MB", "GB"];
+    const i = Math.floor(Math.log(bytes) / Math.log(k));
+    return (bytes / Math.pow(k, i)).toFixed(2) + " " + sizes[i];
+}
+
+// Recuperare health
+async function fetchHealth() {
+    try {
+        const response = await fetch(`${API_BASE}/health`);
+        if (response.ok) {
+            const data = await response.json();
+            return {
+                status: data.status,
+                ollama_status: data.ollama_status,
+                timestamp: new Date().toISOString()
+            };
+        }
+    } catch (error) {
+        console.error("Health check error:", error);
+    }
+    return null;
+}
+
+// Recuperare modelli
+async function fetchModels() {
+    try {
+        const response = await fetch(`${API_BASE}/models`);
+        if (!response.ok) throw new Error("Errore nel caricamento");
+        
+        const data = await response.json();
+        const models = data.models || [];
+        
+        return {
+            models,
+            total: models.length,
+            totalSize: formatBytes(models.reduce((sum, m) => sum + m.size, 0)),
+            timestamp: new Date().toISOString()
+        };
+    } catch (error) {
+        console.error("Error loading models:", error);
+        return null;
+    }
+}
+
+// Sincronizzare i dati
+async function syncData() {
+    const health = await fetchHealth();
+    const modelsData = await fetchModels();
+    
+    // Salvare in localStorage
+    if (health) {
+        localStorage.setItem("llm_monitor_health", JSON.stringify(health));
+    }
+    
+    if (modelsData) {
+        localStorage.setItem("llm_monitor_models", JSON.stringify(modelsData));
+    }
+    
+    // Notificare il main thread
+    self.postMessage({
+        type: "DATA_UPDATED",
+        health,
+        modelsData
+    });
+}
+
+// Eseguire la sincronizzazione iniziale
+syncData();
+
+// Pianificare aggiornamenti periodici
+setInterval(syncData, REFRESH_INTERVAL);
+
+// Gestire messaggi dal main thread
+self.onmessage = (event) => {
+    if (event.data.type === "SYNC_NOW") {
+        syncData();
+    }
+};