docs: add self-hosted deployment guide, Dockerfile & docker-compose.yml

Dockerfile

@@ -0,0 +1,20 @@
+FROM node:20-alpine AS builder
+WORKDIR /app
+COPY package*.json ./
+RUN npm ci
+COPY . .
+ENV NEXT_TELEMETRY_DISABLED=1
+RUN npm run build
+
+FROM node:20-alpine AS runner
+WORKDIR /app
+ENV NODE_ENV=production
+ENV NEXT_TELEMETRY_DISABLED=1
+
+COPY --from=builder /app/package*.json ./
+COPY --from=builder /app/.next ./.next
+COPY --from=builder /app/public ./public
+COPY --from=builder /app/node_modules ./node_modules
+
+EXPOSE 3000
+CMD ["npm", "start"]