feat: Extract Developer Portal as standalone Next.js app on port 3006

SDK customers can now access the documentation publicly without login.
The portal runs independently from admin-v2 on https://macmini:3006/.

- New developer-portal/ app with 26 pages, 2 components
- Docker service + nginx SSL reverse proxy on port 3006
- All /developers/* routes remapped to /* in the new app
- admin-v2 developer pages remain unchanged

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

developer-portal/Dockerfile

@@ -0,0 +1,45 @@
+# Build stage
+FROM node:20-alpine AS builder
+
+WORKDIR /app
+
+# Copy package files
+COPY package.json package-lock.json* ./
+
+# Install dependencies
+RUN npm install
+
+# Copy source code
+COPY . .
+
+# Build the application
+RUN npm run build
+
+# Production stage
+FROM node:20-alpine AS runner
+
+WORKDIR /app
+
+# Set to production
+ENV NODE_ENV=production
+
+# Create non-root user
+RUN addgroup --system --gid 1001 nodejs
+RUN adduser --system --uid 1001 nextjs
+
+# Copy built assets
+COPY --from=builder /app/public ./public
+COPY --from=builder --chown=nextjs:nodejs /app/.next/standalone ./
+COPY --from=builder --chown=nextjs:nodejs /app/.next/static ./.next/static
+
+# Switch to non-root user
+USER nextjs
+
+# Expose port
+EXPOSE 3000
+
+# Set hostname
+ENV HOSTNAME="0.0.0.0"
+
+# Start the application
+CMD ["node", "server.js"]