ci: skip the co-planning dry runs when the Fider token is unavailable

[SnowboardTechie]

Summary

• Stops the two co-planning sync workflows from failing on PRs that run without repository secrets (Dependabot, external forks)
• Time to review: 2 minutes

Changes proposed

• In coplanning-sync-fider-to-gh.yml and coplanning-sync-gh-to-fider.yml, extend the dry-run step's condition from github.event_name == 'pull_request' to also require env.FIDER_API_TOKEN != '', so the step is skipped (not failed) when the token isn't available to the run.

Context for reviewers

Dependabot-triggered pull_request events receive no repository secrets, so on any Dependabot PR touching the co-planning paths the dry run dies with [ERROR] FIDER_API_TOKEN environment variable must be set — both sync checks showed this on #1093. External-fork PRs would hit the same thing, which is why the guard checks token presence rather than the PR author.

Trade-off: a secretless PR that touches these workflows merges without the dry run exercising the change. How fast that surfaces afterward differs by workflow: coplanning-sync-fider-to-gh.yml also runs daily on schedule, so a break there shows up within a day; coplanning-sync-gh-to-fider.yml has only pull_request and workflow_dispatch triggers, so a break there waits for the next manual dispatch.

The real-run steps (workflow_dispatch / schedule) are untouched. The skip can't be reproduced locally or by dispatch (the guard only alters pull_request behavior); the next secretless PR touching these paths is the live validation.

Additional information

The step-level env block maps secrets.FIDER_TOKEN into FIDER_API_TOKEN at the job level, and an unset secret renders as an empty string — which is exactly what the new condition tests.