fix: harden Asana link-check workflow against false rejections and API timeouts

[vishpillai123]

Summary

Two independent issues in the `link-asana-task.yml` reusable workflow, both surfaced while debugging why datakind/edvise-api#282's required `asana` check kept failing:

1. The URL regex rejects a valid, common Asana link shape

The pattern only accepted `app.asana.com/1//project//task/` for current-UI links, but Asana also produces `app.asana.com/1//task/` (no `project//` segment) when a task link is copied from a project-less context — My Tasks, Inbox, search results, etc. That's a completely valid, resolvable Asana permalink, but it silently failed the "must include an Asana task URL" check, forcing PR authors to either dig through a confusing regex or hand-craft a different URL shape.

• Fix: the `project//` segment is now optional in that branch. Verified against all known valid/invalid Asana URL shapes (legacy `/0/...` links, both current-UI link shapes, and non-task workspace/project-only links that should still be rejected).

2. A flaky/slow Asana API call can block merges

The second step (`Asana/create-app-attachment-github-action@v1.3`, which posts a "GitHub PR" attachment widget onto the task — a nicety, not the actual requirement) has no timeout and isn't allowed to fail independently. When Asana's API is slow, this step hangs and times out (`598 Unable to serve response within time limit`), failing the whole required `asana` check even though the PR body already satisfies the real requirement (step 1, the regex check).

• Fix: add `timeout-minutes: 2` and `continue-on-error: true` to that step so it can never block a merge, while leaving the actual requirement (step 1) untouched and still enforced.

Context

Both issues were hit back-to-back on datakind/edvise-api#282:

• For ~17 hours the PR body had `https://app.asana.com/1/6325821815997/task/1216920722472218?focus=true\` (no project segment) and was correctly-but-frustratingly rejected by issue ci: add reusable GitHub workflows and document caller usage #1.
• After the URL was edited to include the project segment, the check kept failing anyway — this time from issue ci: Create and document DataKind shared GitHub workflows #2 (the attachment step timing out against Asana's API).

Test plan

• N/A (workflow-only change). Regex verified locally against all known Asana URL shapes (see PR discussion). Once merged, will verify by re-running the `asana` check on fix: treat campus_name as non-PII column edvise-api#282 (workflow is called via `@main`, so the fix applies immediately without a version bump).