feat: initial monorepo scaffold - Next.js 15 + Prisma + Python SDK stubs

- Turborepo monorepo with apps/web and packages/database, sdk-python
- Next.js 15 app with professional landing page (dark theme, emerald accent)
- Prisma schema: Trace, DecisionPoint, Span, Event models with full indexing
- Docker Compose: web (port 4200), postgres:16, redis:7, migrate service
- Python SDK package stubs: init, trace decorator, log_decision, integrations
- Multi-stage Dockerfile for standalone Next.js production build

Dockerfile

@@ -0,0 +1,26 @@
+FROM node:20-alpine AS base
+RUN apk add --no-cache git
+WORKDIR /app
+
+FROM base AS deps
+COPY package.json package-lock.json* ./
+COPY apps/web/package.json ./apps/web/
+COPY packages/database/package.json ./packages/database/
+RUN npm install --production=false
+
+FROM base AS builder
+COPY --from=deps /app/node_modules ./node_modules
+COPY . .
+RUN npx prisma generate --schema=packages/database/prisma/schema.prisma
+RUN npx turbo build
+
+FROM base AS web
+RUN addgroup --system --gid 1001 nodejs && \
+    adduser --system --uid 1001 nextjs
+COPY --from=builder --chown=nextjs:nodejs /app/apps/web/.next/standalone ./
+COPY --from=builder --chown=nextjs:nodejs /app/apps/web/.next/static ./apps/web/.next/static
+COPY --from=builder --chown=nextjs:nodejs /app/packages/database/prisma ./packages/database/prisma
+USER nextjs
+EXPOSE 3000
+ENV PORT=3000 HOSTNAME="0.0.0.0"
+CMD ["node", "apps/web/server.js"]