build: run the container through dotenvx with the encrypted .env.production

- image installs @dotenvx/dotenvx (pinned) and starts via
  'dotenvx run -f .env.production --strict -- node server.js'
- only DOTENV_PRIVATE_KEY_PRODUCTION is supplied at runtime; without it the
  container exits(1) (MISSING_PRIVATE_KEY) instead of booting with
  undecryptable credentials
- .env.production copied with --chown=node:node (the source mode is 600)
- .dockerignore excludes .env/.env.local/.env.keys so local envs and the
  private keys never enter the build context

Dockerfile

@@ -3,19 +3,29 @@
 # on the field laptop (the wizard reaches it at http://127.0.0.1:9000 from the
 # browser, so the container location does not matter).
 #
+# The encrypted .env.production is baked in; the private key is supplied at
+# runtime and never stored in the image:
+#
 #   docker build -t yreka-tools .
-#   docker run -d -p 4173:4173 --name yreka-tools yreka-tools
+#   docker run -d -p 4173:4173 --name yreka-tools \
+#     --env DOTENV_PRIVATE_KEY_PRODUCTION="$(grep -oP '^DOTENV_PRIVATE_KEY_PRODUCTION=\K.*' .env.keys)" \
+#     yreka-tools
 FROM node:22-alpine
 WORKDIR /app
 
+RUN npm install -g @dotenvx/dotenvx@1.51.4
+
 COPY tools/package.json tools/package-lock.json ./
 RUN npm ci --omit=dev && npm cache clean --force
 
 COPY tools/server.js tools/yrka-auth.js tools/permit.js tools/cropper.js ./
 COPY tools/public ./public
+COPY --chown=node:node .env.production ./
 
 USER node
 EXPOSE 4173
 HEALTHCHECK --interval=30s --timeout=5s --start-period=5s \
   CMD wget -qO- http://127.0.0.1:4173/ >/dev/null || exit 1
-CMD ["node", "server.js"]
+# --strict: fail fast when the private key is missing or decryption fails,
+# instead of starting with unusable credentials.
+CMD ["dotenvx", "run", "-f", ".env.production", "--strict", "--", "node", "server.js"]