Add chat-app and tracing-app deployments

[casey-brooks]

Summary

• add chat-app/tracing-app chart variables, locals, and Helm values
• add Argo CD applications and Istio VirtualServices for new apps
• include chat-app and tracing-app in platform outputs

Testing

• NIXPKGS_ALLOW_UNFREE=1 nix shell --impure nixpkgs#terraform -c terraform -chdir=stacks/platform fmt -check
• NIXPKGS_ALLOW_UNFREE=1 nix shell --impure nixpkgs#terraform -c terraform -chdir=stacks/platform validate

Refs #113

[casey-brooks]

Summary

• add chat-app/tracing-app variables, locals, and Helm values
• add Argo CD applications and Istio VirtualServices for the new apps
• include chat-app and tracing-app in platform outputs

Testing

• NIXPKGS_ALLOW_UNFREE=1 nix shell --impure nixpkgs#terraform -c terraform -chdir=stacks/platform fmt -check
• NIXPKGS_ALLOW_UNFREE=1 nix shell --impure nixpkgs#terraform -c terraform -chdir=stacks/platform validate

Tests: passed 1, failed 0, skipped 0
Lint: terraform fmt -check (no issues)

[noa-lucent]

Clean implementation. All six sections from the issue spec are covered:

• Variables: 4 new variables for chart versions and image tag overrides — consistent with existing naming and structure.
• Locals: Resolved image tags follow the trimspace fallback pattern used by files, notifications, etc. Chart names correct.
• Helm values: Follow the platform_ui_values structure (extraVolumes/extraVolumeMounts for nginx read-only root filesystem). Differences from platform_ui (no ingress, ClusterIP vs NodePort, no probes/env) are intentional per spec.
• ArgoCD applications: Sync wave 25, same depends_on, sync policy, and destination as platform_ui.
• VirtualServices: Subdomain-based routing (chat. / tracing.) with consistent computed_fields and depends_on.
• Outputs: Both apps added to platform_app_names and platform_app_ids.

No correctness, style, or architectural issues found.

[casey-brooks]

Summary

• bump chat-app and tracing-app chart version defaults to v0.1.1

Testing

• NIXPKGS_ALLOW_UNFREE=1 nix shell --impure nixpkgs#terraform -c terraform -chdir=stacks/platform fmt -check
• NIXPKGS_ALLOW_UNFREE=1 nix shell --impure nixpkgs#terraform -c terraform -chdir=stacks/platform validate

Tests: passed 1, failed 0, skipped 0
Lint: terraform fmt -check (no issues)

[noa-lucent]

Re-reviewed after the version bump commit. The only change since my previous (dismissed) approval is the two default bumps in variables.tf:

• chat_app_chart_version: "0.1.0" → "0.1.1"
• tracing_app_chart_version: "0.1.0" → "0.1.1"

All other code (main.tf, outputs.tf) is identical to what I previously approved. No issues.