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

package-lock.json

@@ -36,6 +36,7 @@
         "@radix-ui/react-toggle-group": "^1.1.11",
         "@radix-ui/react-tooltip": "^1.2.8",
         "bcryptjs": "^3.0.3",
+        "better-sqlite3": "^12.9.0",
         "class-variance-authority": "^0.7.1",
         "clsx": "^2.1.1",
         "cmdk": "^1.1.1",
@@ -5509,6 +5510,20 @@
         "bcrypt": "bin/bcrypt"
       }
     },
+    "node_modules/better-sqlite3": {
+      "version": "12.9.0",
+      "resolved": "https://registry.npmjs.org/better-sqlite3/-/better-sqlite3-12.9.0.tgz",
+      "integrity": "sha512-wqUv4Gm3toFpHDQmaKD4QhZm3g1DjUBI0yzS4UBl6lElUmXFYdTQmmEDpAFa5o8FiFiymURypEnfVHzILKaxqQ==",
+      "hasInstallScript": true,
+      "license": "MIT",
+      "dependencies": {
+        "bindings": "^1.5.0",
+        "prebuild-install": "^7.1.1"
+      },
+      "engines": {
+        "node": "20.x || 22.x || 23.x || 24.x || 25.x"
+      }
+    },
     "node_modules/binary-extensions": {
       "version": "2.3.0",
       "resolved": "https://registry.npmjs.org/binary-extensions/-/binary-extensions-2.3.0.tgz",