feat: build multi-arch docker image for connaisseur

[junydania]

Fixes #1984

Description

This PR adds support for building multi-architecture Docker images for Connaisseur, enabling deployment on both AMD64 and ARM64 platforms.

Why?

Currently, Connaisseur Docker images are built only for the host architecture. This limits deployment options, particularly for ARM-based systems such as:

• Apple Silicon (M1/M2/M3 Macs)
• AWS Graviton instances
• ARM-based Kubernetes clusters
• Raspberry Pi and other ARM servers

How?

• Makefile: Added new docker-multiarch target for local multi-platform builds with explicit platform specification (linux/amd64, linux/arm64)
• CI/CD: Updated .github/workflows/101_build.yml to build and push multi-arch images automatically by adding platforms: linux/amd64,linux/arm64 to the build-push-action
• Backward Compatibility: Maintained the existing docker target for single-platform local builds used in development workflows

Checklist

• PR is rebased to/aimed at branch develop
• PR follows Contributing Guide
• Added tests (if necessary) - No new tests needed; existing integration tests cover functionality
• Extended README/Documentation (if necessary) - Makefile comments added; no user-facing documentation changes needed
• Adjusted versions of image and Helm chart in Chart.yaml (if necessary) - Not necessary for this change

[xavidop]

thank you @junydania !

[codecov-commenter]

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.94%. Comparing base (5bda9e1) to head (2fcaedc).
⚠️ Report is 9 commits behind head on develop.
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Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2027      +/-   ##
===========================================
- Coverage    91.37%   90.94%   -0.43%     
===========================================
  Files           35       37       +2     
  Lines         2540     2718     +178     
===========================================
+ Hits          2321     2472     +151     
- Misses         168      189      +21     
- Partials        51       57       +6     

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