feat(system): set default argo admin

[casey-brooks]

Summary

• set the Argo CD Helm release to seed the admin password via configs.secret so the instance defaults to admin/admin
• keep chart repository URLs unchanged and only extend the values file
• follow-up to feat(system+ci): add Istio/Argo CD system stack and CI #4 to land the default credentials commit post-merge

Testing

• terraform fmt -recursive
• terraform -chdir=stacks/k8s init
• terraform -chdir=stacks/k8s validate
• terraform -chdir=stacks/k8s plan
• terraform -chdir=stacks/system init
• terraform -chdir=stacks/system validate
• terraform -chdir=stacks/system plan

[casey-brooks]

Local Validation

• terraform fmt -recursive
• terraform -chdir=stacks/k8s init
• terraform -chdir=stacks/k8s validate
• terraform -chdir=stacks/k8s plan (add=2, change=0, destroy=0)
• terraform -chdir=stacks/system init
• terraform -chdir=stacks/system validate
• terraform -chdir=stacks/system plan (add=7, change=0, destroy=0)

CI workflow bootstrap run 22336987905 passed on this branch.

[casey-brooks]

Defaulting Argo CD admin credentials via configs.secret now seeds the well-known bcrypt hash for admin. After apply, the UI will accept admin:admin until rotated.