Fix: Correct Dockerfile syntax errors in production build

Fixed two syntax errors in the frontend production Dockerfile that were masked by earlier build failures:

1. Line 6: COPY command syntax error
   - Changed: COPY --chown=node:node package.json package.json ./
   - To: COPY --chown=node:node package*.json ./
   - The original attempted to copy package.json twice (invalid syntax)
   - Now uses glob pattern to properly copy package.json and package-lock.json if present
   - Matches the pattern used in backend/Dockerfile.prod:5

2. Lines 15-16: Missing equals signs in ARG and ENV directives
   - Changed: ARG CUSTOM_REQUEST_HEADER nAb3kY-S%qE#4!d
   - To: ARG CUSTOM_REQUEST_HEADER=nAb3kY-S%qE#4!d
   - Changed: ENV REACT_APP_CUSTOM_REQUEST_HEADER $CUSTOM_REQUEST_HEADER
   - To: ENV REACT_APP_CUSTOM_REQUEST_HEADER=$CUSTOM_REQUEST_HEADER
   - Ensures proper Dockerfile syntax compliance

These errors were present in the original file but were not caught because the build was failing earlier due to code issues (duplicate object keys and missing exports) that have been fixed in PR #2086.

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Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

Author: 3 people

client/Dockerfile.prod

@@ -3,7 +3,7 @@ RUN mkdir /srv/client && chown node:node /srv/client
 WORKDIR /srv/client
 USER node
 RUN mkdir -p node_modules
-COPY --chown=node:node package.json package.json ./
+COPY --chown=node:node package*.json ./
 RUN npm install --no-update-notifier
 
 FROM node:20-alpine AS client-builder
@@ -12,8 +12,8 @@ WORKDIR /srv/client
 COPY --from=node-modules-install /srv/client/node_modules node_modules
 COPY . .
 USER root
-ARG CUSTOM_REQUEST_HEADER nAb3kY-S%qE#4!d
-ENV REACT_APP_CUSTOM_REQUEST_HEADER $CUSTOM_REQUEST_HEADER
+ARG CUSTOM_REQUEST_HEADER=nAb3kY-S%qE#4!d
+ENV REACT_APP_CUSTOM_REQUEST_HEADER=$CUSTOM_REQUEST_HEADER
 RUN npm run build
 
 FROM nginx as client-production