LearnSpace: full-stack educational whiteboard platform

Node.js/Express backend + vanilla JS frontend.
Features: real-time collaborative whiteboard (SSE), multi-page support,
LaTeX formulas, shapes/connectors, coordinate systems, number lines,
compass, zoom/pan, Catmull-Rom pencil smoothing, ruler/protractor with
rotation & resize controls, minimap navigation overlay, auto-measurements,
multi-page thumbnails sidebar, PNG export, page templates.
Student/teacher workflows: classes, assignments, library, dashboard.
Mobile responsive. SQLite (better-sqlite3).

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

Dockerfile

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+# ── Stage 1: install production deps ─────────────────────────────────────
+FROM node:22-alpine AS deps
+WORKDIR /app/backend
+COPY backend/package.json backend/package-lock.json ./
+RUN npm ci --omit=dev
+
+# ── Stage 2: runtime ─────────────────────────────────────────────────────
+FROM node:22-alpine
+LABEL maintainer="BQ-System"
+
+RUN apk add --no-cache sqlite tini
+
+WORKDIR /app
+COPY --from=deps /app/backend/node_modules ./backend/node_modules
+COPY backend/package.json ./backend/
+COPY backend/src           ./backend/src
+COPY backend/seed.js       ./backend/seed.js
+COPY frontend              ./frontend
+COPY js                    ./js
+
+# Ensure data & uploads dirs exist (volumes mount here)
+RUN mkdir -p /app/backend/data /app/backend/uploads /app/backups
+
+ENV NODE_ENV=production
+ENV PORT=3000
+EXPOSE 3000
+
+HEALTHCHECK --interval=30s --timeout=5s --start-period=10s --retries=3 \
+  CMD wget -qO- http://localhost:3000/api/health || exit 1
+
+ENTRYPOINT ["tini", "--"]
+CMD ["node", "backend/src/server.js"]