feat: notify ops repo on version tag releases

[noahsaso]

Adds a notify-ops job to the Docker build workflow that sends a repository_dispatch event to the ops repo when a version tag (v*) is pushed.

This enables automated version tracking — when a new argus release is tagged and its Docker image is built, the ops repo is notified so it can update the chain version config automatically.

What it does

• Fires only on refs/tags/v* pushes (not branch pushes or PRs)
• Sends {repo, tag, sha} payload to the ops repo's auto-upgrade.yml workflow
• Requires OPS_REPO_PAT secret (fine-grained PAT with contents: write on the ops repo)

Setup

Add OPS_REPO_PAT as a repository secret — a fine-grained GitHub PAT scoped to contents: write on NoahSaso/intentional-design-ops.

[noahsaso]

No longer needed — ops repo now polls for new tags instead of requiring repository_dispatch from fork CI. Zero changes needed in argus or fork repos.