Configure comprehensive Copilot instructions for repository best practices - #923

Enhanced .github/copilot-instructions.md to provide complete context for AI coding agents per GitHub Copilot best practices.

Added Sections

• Overview & Technology Stack - Electron 29.x + React 16.x + TypeScript architecture with mqttjs, Redux, Material-UI
• Code Style - TSLint (Airbnb), Prettier config: no semicolons, single quotes, 2-space indent, trailing commas
• Dependency Management - Monorepo structure guidance (root/app/backend package.json), frozen lockfile usage
• Debugging - Development mode workflows, source map usage, common issues (build failures, MQTT broker requirements)
• Deployment - Semantic release automation, beta/production branch workflow, multi-platform build artifacts

Enhanced Sections

• Important Notes - Node.js ≥18 requirement, workspace-like monorepo structure
• TypeScript Guidelines - Strict null checks, interface usage, const over let

The instructions now cover setup, testing (with MQTT async handling), code conventions, dependency management, debugging, and release processes - providing AI agents with sufficient context for accurate code suggestions aligned with project patterns.

• Fixes ✨ Set up Copilot instructions #922

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.