feat: P3 batch 1 - context menus, shortcuts, connection management

- Key list right-click context menu (copy/delete/export/memory/copy value)
- Shift+Click range selection + Select All checkbox
- Keyboard shortcuts: Ctrl+, (settings), Ctrl+S (save), Ctrl+L (clear CLI), Ctrl+/ (hotkeys help)
- CLI auto-sync: SELECT updates DB, write commands refresh key list
- Connection color marking (6 predefined colors)
- Duplicate connection button
- Connection drag-and-drop reorder (native HTML5)
- i18n keys for all features (zh-CN + en)

src/stores/connection.ts

@@ -41,6 +41,7 @@ export const useConnectionStore = defineStore('connection', () => {
   const error = ref<string | null>(null)
   const serverInfoMap = ref<Record<string, string>>({})
   const healthMap = ref<Record<string, boolean>>({})
+  const currentDb = ref<number>(0)
   const healthTimers = new Map<string, ReturnType<typeof setInterval>>()
 
   const activeConnection = computed(() =>
@@ -273,7 +274,7 @@ export const useConnectionStore = defineStore('connection', () => {
   }
 
   return {
-    connections, activeId, connectedIds, connecting, error, serverInfo, healthOk,
+    connections, activeId, connectedIds, connecting, error, serverInfo, healthOk, currentDb,
     activeConnection, isConnected,
     loadConnections, decryptPassword, getInfo, saveConnection, deleteConnection, reorderConnections,
     connect, disconnect, disconnectById, switchTo, isConnectedById, testConnection, exportConnections, importConnections,