Add local Kubernetes deployment environment (kind + Podman + Argo CD) - #1505

Description

• Adds a complete local Kubernetes development environment for Overleaf Community Edition under a k8s/ directory.
• Uses kind with Podman as the container runtime and Argo CD for GitOps-style deployment.
• All runtime images are built locally and served from a local OCI registry inside kind (localhost:5001) - the environment is fully sandboxed following bootstrap.
• No existing files in the source tree are modified.
• Built and tested on macOS using homebrew, but installation steps should be straightforward to tailor for other platforms.

Contents

• Bootstrap/teardown scripts (k8s/bootstrap/01-06): check and/or install prerequisites for macOS, create a kind cluster, stand up a local registry, install Argo CD, build and push all images, and tear down.
• Helm chart (k8s/charts/overleaf/): deploys Overleaf (NodePort 30000), MongoDB 8.0 (with replica-set init), and Redis 6.2, each with persistent volume claims.
• Argo CD configuration (k8s/argocd/): an Application pointing at the Helm chart with auto-sync and self-heal enabled.
• Documentation (k8s/README.md): architecture overview.

Warning

Before this change can be approved, repoURL will need to change in k8s/argocd/application.yaml. It should point to:

repoURL: https://github.com/overleaf/overleaf.git

I have left this pointing to a fork for now to allow for testing.

Related issues / Pull Requests

N/A

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