fix: add error logging for node state writes and queries

Silent error swallowing made it impossible to diagnose why worker
couldn't see master's heartbeat. Now logs errors from:
- updateNodeState upsert failures
- writeStateToSharedMariaDB connection/write failures
- getNodeStatesShared query failures
- list endpoint shows state count in logs

Also improved First() call to not overwrite state on error.

Bump version to v1.6.5.

config/version

@@ -1 +1 @@
-v1.6.4
+v1.6.5

web/controller/node.go

@@ -1,6 +1,7 @@
 package controller
 
 import (
+	"log"
 	"os"
 	"strconv"
 	"time"
@@ -48,13 +49,18 @@ type NodeView struct {
 func getNodeStatesFromShared() ([]model.NodeState, error) {
 	// If current DB is already MariaDB, use it directly
 	if config.GetDBTypeFromJSON() == "mariadb" {
-		return database.GetNodeStates()
+		states, err := database.GetNodeStates()
+		if err != nil {
+			log.Printf("[NodeList] GetNodeStates error: %v", err)
+		}
+		return states, err
 	}
 
 	// Otherwise, open a temporary connection to the shared MariaDB
 	dbConfig := config.GetDBConfigFromJSON()
 	db, err := database.OpenMariaDB(dbConfig)
 	if err != nil {
+		log.Printf("[NodeList] failed to open shared MariaDB: %v", err)
 		return nil, err
 	}
 	sqlDB, _ := db.DB()
@@ -62,6 +68,9 @@ func getNodeStatesFromShared() ([]model.NodeState, error) {
 
 	var states []model.NodeState
 	err = db.Order("node_id").Find(&states).Error
+	if err != nil {
+		log.Printf("[NodeList] failed to query shared MariaDB node_states: %v", err)
+	}
 	return states, err
 }
 
@@ -73,6 +82,7 @@ func (a *NodeController) list(c *gin.Context) {
 		jsonMsg(c, "get node states", err)
 		return
 	}
+	log.Printf("[NodeList] role=%s nodeId=%s, found %d states in shared DB", nodeCfg.Role, nodeCfg.NodeID, len(states))
 
 	syncInterval := nodeCfg.SyncIntervalSeconds
 	if syncInterval <= 0 {

web/service/node_sync.go

@@ -3,6 +3,7 @@ package service
 import (
 	"context"
 	"errors"
+	"log"
 	"os"
 	"time"
 
@@ -45,7 +46,10 @@ func (s *NodeSyncService) updateNodeState(version int64, syncErr error, didSync
 	}
 	now := time.Now().Unix()
 	state := &model.NodeState{}
-	_ = database.GetDB().First(state, "node_id = ?", nodeCfg.NodeID).Error
+	if err := database.GetDB().First(state, "node_id = ?", nodeCfg.NodeID).Error; err != nil {
+		// First heartbeat — record doesn't exist yet, that's OK
+		state = &model.NodeState{}
+	}
 	state.NodeID = nodeCfg.NodeID
 	state.NodeRole = string(nodeCfg.Role)
 	state.LastHeartbeatAt = now
@@ -58,7 +62,9 @@ func (s *NodeSyncService) updateNodeState(version int64, syncErr error, didSync
 	} else {
 		state.LastError = ""
 	}
-	_ = database.UpsertNodeState(database.GetDB(), state)
+	if err := database.UpsertNodeState(database.GetDB(), state); err != nil {
+		log.Printf("[NodeSync] failed to upsert node state for %s: %v", nodeCfg.NodeID, err)
+	}
 
 	// Master also writes heartbeat to shared MariaDB so workers can see it
 	if nodeCfg.Role == config.NodeRoleMaster {
@@ -78,11 +84,14 @@ func (s *NodeSyncService) writeStateToSharedMariaDB(state *model.NodeState) {
 	}
 	sharedDB, err := database.OpenMariaDB(dbConfig)
 	if err != nil {
+		log.Printf("[NodeSync] failed to open shared MariaDB for heartbeat: %v", err)
 		return
 	}
 	sqlDB, _ := sharedDB.DB()
 	defer sqlDB.Close()
-	_ = database.UpsertNodeState(sharedDB, state)
+	if err := database.UpsertNodeState(sharedDB, state); err != nil {
+		log.Printf("[NodeSync] failed to upsert node state to shared MariaDB: %v", err)
+	}
 }
 
 func (s *NodeSyncService) BootstrapFromCache() error {