refactor: adopt POSITIONS constants, fix ESLint warnings, break menuUtils into modules

- Replace hardcoded position strings with POSITIONS.* constants
- Prefix unused variables with _ to resolve no-unused-vars warnings
- Fix no-prototype-builtins with Object.prototype.hasOwnProperty.call()
- Extract menuUtils.js (543 lines) into 6 focused modules under menu/
- menuUtils.js now 35 lines, delegates via prototype mixin pattern
- Add 158 unit tests for ConfigManager, MeasurementContainer, ValidationUtils

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/helper/outputUtils.js

@@ -9,7 +9,7 @@ class OutputUtils {
   checkForChanges(output, format) {
     const changedFields = {};
     for (const key in output) {
-      if (output.hasOwnProperty(key) && output[key] !== this.output[format][key]) {
+      if (Object.prototype.hasOwnProperty.call(output, key) && output[key] !== this.output[format][key]) {
         let value = output[key];
         // For fields: if the value is an object (and not a Date), stringify it.
         if (value !== null && typeof value === 'object' && !(value instanceof Date)) {
@@ -81,13 +81,13 @@ class OutputUtils {
   flattenTags(obj) {
     const result = {};
     for (const key in obj) {
-      if (obj.hasOwnProperty(key)) {
+      if (Object.prototype.hasOwnProperty.call(obj, key)) {
         const value = obj[key];
         if (value !== null && typeof value === 'object' && !(value instanceof Date)) {
           // Recursively flatten the nested object.
           const flatChild = this.flattenTags(value);
           for (const childKey in flatChild) {
-            if (flatChild.hasOwnProperty(childKey)) {
+            if (Object.prototype.hasOwnProperty.call(flatChild, childKey)) {
               result[`${key}_${childKey}`] = String(flatChild[childKey]);
             }
           }