🐛 fix(cli): robust npx entry point, Node 20 requirement, setup hardening (#8)

- Use fs.realpathSync for entry point detection to fix npx symlink failures
- Add --help and --version CLI flags with explicit process.exit(0)
- Add TTY detection in setup wizard to prevent non-interactive hangs
- Wrap JSON.parse in mergeJsonConfig with try/catch for malformed configs
- Update engines.node to >=20.0.0 to match better-sqlite3 requirements
- Update Dockerfiles from node:18-slim to node:20-slim
- Remove error-swallowing || true from postinstall script
- Replace deprecated windows-build-tools with VS Build Tools link

Dockerfile.canvas

@@ -2,7 +2,7 @@
 # Provides the web interface, REST API, and SQLite persistence
 
 # Stage 1: Build frontend
-FROM node:18-slim AS frontend-builder
+FROM node:20-slim AS frontend-builder
 
 WORKDIR /app
 
@@ -14,7 +14,7 @@ COPY vite.config.js ./
 RUN npm run build:frontend
 
 # Stage 2: Build backend (TypeScript compilation + native modules)
-FROM node:18-slim AS backend-builder
+FROM node:20-slim AS backend-builder
 
 RUN apt-get update && apt-get install -y python3 make g++ && rm -rf /var/lib/apt/lists/*
 
@@ -28,7 +28,7 @@ COPY tsconfig.json ./
 RUN npm run build:server
 
 # Stage 3: Production Canvas Server
-FROM node:18-slim AS production
+FROM node:20-slim AS production
 
 RUN apt-get update && apt-get install -y python3 make g++ && rm -rf /var/lib/apt/lists/*