refactor: JS served vanilla, no more NPM or Express

Dockerfile

@@ -2,17 +2,6 @@ FROM node:20-alpine
 
 WORKDIR /app
 
-# The npm version bundled with node:20-alpine has a known "Exit handler
-# never called!" bug under slow/unreliable networks (common on VPS hosts).
-# Upgrading npm first, plus more tolerant retry/timeout settings, avoids it.
-RUN npm install -g npm@11 \
-  && npm config set fetch-retries 5 \
-  && npm config set fetch-retry-mintimeout 20000 \
-  && npm config set fetch-timeout 300000
-
-COPY package.json package-lock.json ./
-RUN npm ci --omit=dev && node -e "require('express')"
-
 COPY server.js ./
 COPY src ./src
 COPY public ./public