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>

Dockerfile.e2e

@@ -0,0 +1,18 @@
+FROM nodered/node-red:latest
+
+WORKDIR /usr/src/node-red
+
+# Copy package files and nodes source
+COPY package.json ./
+COPY nodes/ ./nodes/
+
+# Rewrite generalFunctions dependency from git+https to local file path
+RUN sed -i 's|"generalFunctions": "git+https://[^"]*"|"generalFunctions": "file:./nodes/generalFunctions"|' package.json
+
+# Install dependencies (ignore scripts to avoid postinstall git checkout)
+RUN npm install --ignore-scripts
+
+# Copy test flows into Node-RED data directory
+COPY test/e2e/flows.json /data/flows.json
+
+EXPOSE 1880