chore: add Docker/nginx setup for Coolify deployment

- Add multi-stage Dockerfile (Node 24 + pnpm builder, nginx:alpine server)
- Add nginx.conf with SPA routing and asset caching
- Remove netlify.toml

Dockerfile

@@ -0,0 +1,17 @@
+FROM node:24-alpine AS builder
+
+RUN corepack enable && corepack prepare pnpm@latest --activate
+
+WORKDIR /app
+COPY package.json pnpm-lock.yaml ./
+RUN pnpm install --frozen-lockfile
+
+COPY . .
+RUN pnpm build-only
+
+FROM nginx:alpine
+
+COPY nginx.conf /etc/nginx/conf.d/default.conf
+COPY --from=builder /app/dist /usr/share/nginx/html
+
+EXPOSE 80