Fix security scan issues and harden docker-compose

Hadolint fixes:
- Use printf instead of echo for escape sequences
- Add hadolint ignore for apt pin version (DL3008)

KICS fixes (docker-compose):
- Add security_opt: no-new-privileges to all services
- Add mem_limit and cpus to prevent resource exhaustion
- Add healthcheck to orchard-server in docker-compose.yml

Gitleaks:
- Add .gitleaksignore for false positive (s3_key attribute name)
- Remove allow_failure from secrets job (now blocking)

Also:
- Remove || echo fallback from python_tests (tests should fail pipeline)

Dockerfile

@@ -22,9 +22,10 @@ RUN npm run build
 FROM containers.global.bsf.tools/python:3.12-slim
 
 # Disable proxy cache
-RUN echo 'Acquire::http::Pipeline-Depth 0;\nAcquire::http::No-Cache true;\nAcquire::BrokenProxy true;\n' > /etc/apt/apt.conf.d/99fixbadproxy
+RUN printf 'Acquire::http::Pipeline-Depth 0;\nAcquire::http::No-Cache true;\nAcquire::BrokenProxy true;\n' > /etc/apt/apt.conf.d/99fixbadproxy
 
 # Install system dependencies
+# hadolint ignore=DL3008
 RUN apt-get update && apt-get install -y --no-install-recommends \
     curl \
     && rm -rf /var/lib/apt/lists/*