feat: Initial Hub Dashboard with email, calendar, and tasks

AI-powered unified business workspace for LetsBe Cloud tenants.
- Next.js 15 (App Router) with Keycloak SSO via NextAuth.js v5
- Email client: IMAP/SMTP via ImapFlow + nodemailer (inbox, compose, search, folders)
- Calendar: CalDAV via tsdav + Schedule-X (month/week/day views, event CRUD)
- Task management: Vikunja API integration (list view, kanban, filters)
- Responsive shell with sidebar navigation and activity feed
- Docker deployment ready

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

Dockerfile

@@ -0,0 +1,44 @@
+# Stage 1: Install dependencies
+FROM node:20-alpine AS deps
+WORKDIR /app
+COPY package.json package-lock.json* ./
+RUN npm ci --only=production
+
+# Stage 2: Build
+FROM node:20-alpine AS builder
+WORKDIR /app
+COPY --from=deps /app/node_modules ./node_modules
+COPY . .
+
+ENV NEXT_TELEMETRY_DISABLED=1
+
+RUN npm run build
+
+# Stage 3: Production
+FROM node:20-alpine AS runner
+WORKDIR /app
+
+ENV NODE_ENV=production
+ENV NEXT_TELEMETRY_DISABLED=1
+
+RUN addgroup --system --gid 1001 nodejs
+RUN adduser --system --uid 1001 nextjs
+
+COPY --from=builder /app/public ./public
+
+# Set the correct permissions for prerender cache
+RUN mkdir .next
+RUN chown nextjs:nodejs .next
+
+# Automatically leverage output traces to reduce image size
+COPY --from=builder --chown=nextjs:nodejs /app/.next/standalone ./
+COPY --from=builder --chown=nextjs:nodejs /app/.next/static ./.next/static
+
+USER nextjs
+
+EXPOSE 3002
+
+ENV PORT=3002
+ENV HOSTNAME="0.0.0.0"
+
+CMD ["node", "server.js"]