Fix: solucionar error SQLITE_BUSY y mejorar backend

- Migrar de sqlite3 a better-sqlite3 con conexión persistente
- Configurar WAL mode, busy_timeout y PRAGMAs optimizados
- Implementar transacciones para operaciones bulk
- Corregir error initialLoadComplete en useHospitalStore.ts
- Agregar tablas usuarios y kv faltantes
- Actualizar .gitignore para archivos WAL de SQLite

src/hooks/useHospitalStore.ts

@@ -111,33 +111,61 @@ export function useHospitalStore() {
     return () => { mounted = false; };
   }, []);
 
-  // Persist state to backend when it changes (debounced)
-  const [initialLoadComplete, setInitialLoadComplete] = useState(false);
+  // Persistence: event-driven + periodic save
+  const [saveQueue, setSaveQueue] = useState<string[]>([]);
+  const [isSaving, setIsSaving] = useState(false);
   
-  useEffect(() => {
-    if (isLoaded && !initialLoadComplete) {
-      setInitialLoadComplete(true);
-    }
-  }, [isLoaded, initialLoadComplete]);
-
-  useEffect(() => {
-    if (!initialLoadComplete) return;
-    const t = setTimeout(() => {
-      (async () => {
-        try {
-          const { currentUser, isAuthenticated, ...stateToSave } = state;
-          await fetch(`${API_BASE}/state`, {
-            method: 'PUT',
-            headers: { 'Content-Type': 'application/json' },
-            body: JSON.stringify(stateToSave),
-          });
-        } catch (err) {
-          // ignore save errors for now
+  // Track which parts changed
+  const [changedKeys, setChangedKeys] = useState<Set<string>>(new Set());
+  
+  // Mark parts as changed
+  const markChanged = (key: string) => {
+    setChangedKeys(prev => {
+      const next = new Set(prev);
+      next.add(key);
+      return next;
+    });
+  };
+  
+  // Save only changed parts
+  const saveChanges = useCallback(async () => {
+    if (isSaving || changedKeys.size === 0) return;
+    setIsSaving(true);
+    try {
+      const keysToSave = Array.from(changedKeys);
+      const partialState: any = {};
+      keysToSave.forEach(key => {
+        if (key in state) {
+          partialState[key] = state[key];
         }
-      })();
-    }, 300);
-    return () => clearTimeout(t);
-  }, [state, initialLoadComplete]);
+      });
+      
+      await fetch(`${API_BASE}/state/partial`, {
+        method: 'PUT',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify(partialState),
+      });
+      setChangedKeys(new Set());
+    } catch (err) {
+      console.error('Save error:', err);
+    } finally {
+      setIsSaving(false);
+    }
+  }, [state, changedKeys, isSaving]);
+
+  // Periodic save every 5 seconds if there are changes
+  useEffect(() => {
+    if (!isLoaded) return;
+    const t = setInterval(() => {
+      saveChanges();
+    }, 5000);
+    return () => clearInterval(t);
+  }, [isLoaded, saveChanges]);
+  
+  // Also save on特定 events (optional)
+  const queueSave = (keys: string[]) => {
+    keys.forEach(markChanged);
+  };
 
   // Utility functions
   const getCamaAreaId = useCallback((camaId: string): string | null => {