fix: guard docker-entrypoint sed against empty env vars

[lupita-hom]

Problem

Commit f899d10 added docker-entrypoint.sh as the container ENTRYPOINT to support runtime API URL replacement. However, the script unconditionally runs sed to replace the build-time URL defaults (http://localhost/api, ws://localhost) with the values of REACT_APP_API_URL and REACT_APP_WEBSOCKET_URL.

When running via docker-compose, the client service does not pass these as runtime env vars (they are only build ARGs). So at container startup:

• REACT_APP_API_URL → empty string
• REACT_APP_WEBSOCKET_URL → empty string

The sed replaces all API URLs in the JS bundle with empty strings. Every fetch() call then hits "" → resolves to the nginx root → returns index.html (HTML) instead of JSON → the app crashes with TypeError: undefined is not an object (evaluating 'd.map') on every page that makes API calls (Settings, Dashboard, etc.).

Root Cause

# OLD (always runs, even when vars are empty):
sed -i -e "s|http://localhost/api|${REACT_APP_API_URL}|g" "$file"
#                                  ^^^^^^^^^^^^^^^^^^^^^^^^
#                                  Empty → replaces URLs with nothing

Fix

Only run the sed replacement when the env vars are actually set (non-empty). When not set, the build-time defaults remain intact and work correctly with the existing nginx.conf proxy_pass to server:5001.

# NEW (guarded):
if [ -n "${REACT_APP_API_URL}" ]; then
  sed -i "s|http://localhost/api|${REACT_APP_API_URL}|g" "$file"
fi

Also added:

• set -e for fail-fast behavior
• File existence check ([ -f "$file" ]) to avoid errors on empty glob
• Clear startup logging for debugging
• Proper newline at end of file

Testing

Docker Compose (default — no runtime env vars):

docker compose up --build -d
# Settings page loads ✅
# API calls return JSON ✅
# No sed replacement runs (build defaults preserved)

Kubernetes / custom deployment (with runtime env vars):

docker run -e REACT_APP_API_URL=https://myhost.com/api \
           -e REACT_APP_WEBSOCKET_URL=wss://myhost.com \
           -p 8080:80 runwatch-client:fix
# URLs replaced at startup ✅
# API calls route to custom host ✅

Fixes regression from f899d10.

[github-actions]

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Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

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