feat: add exchange account states and refine beginner trader creation flow (#1450)

* feat: implement exchange account state management and UI updates

- Added functionality to invalidate exchange account state cache on exchange config updates, creation, and deletion.
- Introduced new API endpoint to fetch exchange account states.
- Updated frontend components to display exchange account states, including status and balance information.
- Enhanced user experience by refreshing exchange account states after relevant actions.

* feat: enhance trader creation readiness in AITradersPage and BeginnerGuideCards

---------

Co-authored-by: Dean <afei.wuhao@gmail.com>

api/handler_exchange.go

@@ -192,6 +192,8 @@ func (s *Server) handleUpdateExchangeConfigs(c *gin.Context) {
 		}
 	}
 
+	s.exchangeAccountStateCache.Invalidate(userID)
+
 	// Remove affected traders from memory BEFORE reloading to pick up new config
 	for traderID := range tradersToReload {
 		logger.Infof("🔄 Removing trader %s from memory to reload with new exchange config", traderID)
@@ -284,6 +286,8 @@ func (s *Server) handleCreateExchange(c *gin.Context) {
 		return
 	}
 
+	s.exchangeAccountStateCache.Invalidate(userID)
+
 	logger.Infof("✓ Created exchange account: type=%s, name=%s, id=%s", req.ExchangeType, req.AccountName, id)
 	c.JSON(http.StatusOK, gin.H{
 		"message": "Exchange account created",
@@ -327,6 +331,8 @@ func (s *Server) handleDeleteExchange(c *gin.Context) {
 		return
 	}
 
+	s.exchangeAccountStateCache.Invalidate(userID)
+
 	logger.Infof("✓ Deleted exchange account: id=%s", exchangeID)
 	c.JSON(http.StatusOK, gin.H{"message": "Exchange account deleted"})
 }