fix(ci): make infra-plan dependency optional for API/web pipelines

infra-apply needs infra-plan, but infra-plan only runs when infra/**
changes. API/web-triggered pipelines fail to create because the
dependency doesn't exist. Adding optional: true allows infra-apply
to run without infra-plan for manual triggers.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitlab-ci.yml

@@ -1197,6 +1197,7 @@ infra-apply:
     - docker
   needs:
     - job: infra-plan
+      optional: true
   rules:
     - if: $CI_COMMIT_BRANCH == "main" && $CI_PIPELINE_SOURCE == "push"
       changes: