Python 3.14.3 and PHP 8.5.3

What's Changed

• Bump actions/checkout from 6.0.1 to 6.0.2 by @dependabot[bot] in #65
• Dockerfile: "hardcode" image tags so that dependabot can update them automatically by @macbre in #66
• Bump python from 3.14.2-alpine to 3.14.3-alpine by @dependabot[bot] in #67
• Bump composer from 2.9.3 to 2.9.5 by @dependabot[bot] in #68
• Bump php from 8.5.1-cli-alpine to 8.5.3-cli-alpine by @dependabot[bot] in #69

Full Changelog: v3.14.2-8.5.1...v3.14.3-8.5.3