feat: architecture refactor — validators, positions, menuUtils, ESLint, tests, CI

Major improvements across the codebase:

- Extract validationUtils.js (548→217 lines) into strategy pattern validators
- Extract menuUtils.js (543→35 lines) into 6 focused menu modules
- Adopt POSITIONS constants across 23 files (183 replacements)
- Eliminate all 71 ESLint warnings (0 errors, 0 warnings)
- Add 158 unit tests for ConfigManager, MeasurementContainer, ValidationUtils
- Add architecture documentation with Mermaid diagrams
- Add CI pipeline (Docker, ESLint, Jest, Makefile)
- Add E2E infrastructure (docker-compose.e2e.yml)

Test results: 377 total (230 Jest + 23 node:test + 124 legacy), all passing
Lint: 0 errors, 0 warnings

Closes #2, #3, #9, #13, #14, #18

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

eslint.config.js

@@ -0,0 +1,29 @@
+const js = require('@eslint/js');
+const globals = require('globals');
+
+module.exports = [
+  js.configs.recommended,
+  {
+    languageOptions: {
+      ecmaVersion: 2022,
+      sourceType: 'commonjs',
+      globals: {
+        ...globals.node,
+        ...globals.jest,
+        RED: 'readonly',
+      },
+    },
+    rules: {
+      'no-unused-vars': ['warn', { argsIgnorePattern: '^_', varsIgnorePattern: '^_' }],
+      'no-console': 'off',
+      'no-prototype-builtins': 'warn',
+      'no-constant-condition': 'warn',
+    },
+  },
+  {
+    ignores: [
+      'node_modules/**',
+      'nodes/generalFunctions/src/coolprop-node/coolprop/**',
+    ],
+  },
+];