feat: update CI workflows and add release management configuration

[almog8k]

Question	Answer
CI	✔

Overview

This PR modernizes the CI/CD pipeline by adopting shared workflows, adding automated releases, and improving code quality checks.

Changes

Build & Push Workflow (build_and_push.yml)

• Migrated to MapColonies shared workflow actions
• Builds and pushes both tiles-merger-service and tiles-merger-cli Docker images
• Builds and pushes Helm chart
• Updates artifacts file for Docker and Helm
• Triggers on v* tags only

Release Please (New)

• release-please.yml - Automated release workflow
• release-please-config.json - Configuration with Helm chart version updates
• .release-please-manifest.json - Version tracking (starting at 2.1.7)

Pull Request Workflow (pull_request.yaml)

• Updated all action versions (checkout@v6, setup-dotnet@v4, upload-artifact@v4)
• Migrated Docker builds to docker/build-push-action@v6

Dependabot (dependabot.yaml)

• NuGet packages (grouped: OpenTelemetry, Microsoft, AWS, patch updates)
• Docker base images (MergerService, MergerCli)
• GitHub Actions versions