feat: harden production containers

[CryptoJones]

Summary

• add a standalone production compose stack with no published Postgres port and required deployment configuration
• run API and poller images as non-root users with read-only filesystems, dropped capabilities, no-new-privileges, and bounded tmpfs scratch space
• pin production deployments to released images and document secret generation, TLS proxying, and safe startup
• add regression checks for the container hardening contract
• bump both runtime versions to 1.12.0

Validation

• 63 Python tests passed; Ruff, strict mypy, and Bandit clean
• 191 .NET tests passed
• 12 Playwright tests passed; 2 expected skips
• API and poller images built successfully
• hardened image smoke tests confirmed non-root UIDs 1654 and 10001
• production compose validation passed and refuses missing required values
• npm, NuGet, and pip-audit report no known vulnerabilities
• uv lock check clean

Closes #53

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📥 Commits

Reviewing files that changed from the base of the PR and between 6b2f262 and 11c4d0c.

⛔ Files ignored due to path filters (1)

• uv.lock is excluded by !**/*.lock

📒 Files selected for processing (11)

• .env.production.example
• .github/workflows/release.yml
• .gitignore
• BACKLOG.md
• Dockerfile.poller
• README.md
• api/ApplyTrack.Api/ApplyTrack.Api.csproj
• api/ApplyTrack.Api/Dockerfile
• docker-compose.production.yml
• pyproject.toml
• tests/test_containers.py

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