✨ feat(sync): 数据同步支持差异对比、行级选择与实时进度日志

- 新增差异分析/预览接口与前端预览抽屉（插入/更新/删除）
  - 支持按表勾选插入/更新/删除（删除默认不勾选）
  - 支持按主键选择行级同步；无主键/复合主键表跳过并提示
  - 同步过程实时输出中文日志与进度条，便于定位失败步骤

internal/sync/sql_helpers.go

@@ -0,0 +1,109 @@
+package sync
+
+import "strings"
+
+func normalizeSyncMode(mode string) string {
+	m := strings.ToLower(strings.TrimSpace(mode))
+	switch m {
+	case "", "insert_update":
+		return "insert_update"
+	case "insert_only":
+		return "insert_only"
+	case "full_overwrite":
+		return "full_overwrite"
+	default:
+		return "insert_update"
+	}
+}
+
+func quoteIdentByType(dbType string, ident string) string {
+	if ident == "" {
+		return ident
+	}
+
+	switch dbType {
+	case "mysql":
+		return "`" + strings.ReplaceAll(ident, "`", "``") + "`"
+	default:
+		return `"` + strings.ReplaceAll(ident, `"`, `""`) + `"`
+	}
+}
+
+func quoteQualifiedIdentByType(dbType string, ident string) string {
+	raw := strings.TrimSpace(ident)
+	if raw == "" {
+		return raw
+	}
+
+	parts := strings.Split(raw, ".")
+	if len(parts) <= 1 {
+		return quoteIdentByType(dbType, raw)
+	}
+
+	quotedParts := make([]string, 0, len(parts))
+	for _, part := range parts {
+		part = strings.TrimSpace(part)
+		if part == "" {
+			continue
+		}
+		quotedParts = append(quotedParts, quoteIdentByType(dbType, part))
+	}
+
+	if len(quotedParts) == 0 {
+		return quoteIdentByType(dbType, raw)
+	}
+	return strings.Join(quotedParts, ".")
+}
+
+func normalizeSchemaAndTable(dbType string, dbName string, tableName string) (string, string) {
+	rawTable := strings.TrimSpace(tableName)
+	rawDB := strings.TrimSpace(dbName)
+	if rawTable == "" {
+		return rawDB, rawTable
+	}
+
+	if parts := strings.SplitN(rawTable, ".", 2); len(parts) == 2 {
+		schema := strings.TrimSpace(parts[0])
+		table := strings.TrimSpace(parts[1])
+		if schema != "" && table != "" {
+			return schema, table
+		}
+	}
+
+	switch strings.ToLower(strings.TrimSpace(dbType)) {
+	case "postgres", "kingbase":
+		return "public", rawTable
+	default:
+		return rawDB, rawTable
+	}
+}
+
+func qualifiedNameForQuery(dbType string, schema string, table string, original string) string {
+	raw := strings.TrimSpace(original)
+	if raw == "" {
+		return raw
+	}
+	if strings.Contains(raw, ".") {
+		return raw
+	}
+
+	switch strings.ToLower(strings.TrimSpace(dbType)) {
+	case "postgres", "kingbase":
+		s := strings.TrimSpace(schema)
+		if s == "" {
+			s = "public"
+		}
+		if table == "" {
+			return raw
+		}
+		return s + "." + table
+	case "mysql":
+		s := strings.TrimSpace(schema)
+		if s == "" || table == "" {
+			return table
+		}
+		return s + "." + table
+	default:
+		return table
+	}
+}