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

@@ -0,0 +1,20 @@
+FROM node:20-slim
+
+WORKDIR /app
+
+# Copy package files first for layer caching
+COPY package.json package-lock.json ./
+
+# Copy generalFunctions submodule (needed as local dependency)
+COPY nodes/generalFunctions/ ./nodes/generalFunctions/
+
+# Rewrite git+https dependency to local path (avoids needing Gitea credentials)
+RUN sed -i 's|"generalFunctions": "git+https://[^"]*"|"generalFunctions": "file:./nodes/generalFunctions"|' package.json
+
+RUN npm install --ignore-scripts
+
+# Copy full source
+COPY . .
+
+# Default: run full CI suite
+CMD ["npm", "run", "ci"]