UI: Avoid 404 links for tasks outside run dates

[deepujain]

Tasks excluded from a Dag run by their start or end date still appear as placeholders in the Grid and Graph views, but no TaskInstance exists for them. Route those placeholders to the task overview instead of a run-level TaskInstance endpoint that returns 404.

Regression coverage verifies placeholder navigation in the link component, Graph nodes, and Grid cells.

closes: #71761

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[github-actions]

Backport failed to create: v3-3-test. View the failure log Run details

Note: As of Merging PRs targeted for Airflow 3.X
the committer who merges the PR is responsible for backporting the PRs that are bug fixes (generally speaking) to the maintenance branches.

In matter of doubt please ask in #release-management Slack channel.

Status	Branch	Result
❌	v3-3-test

You can attempt to backport this manually by running:

cherry_picker 45fa44f v3-3-test

This should apply the commit to the v3-3-test branch and leave the commit in conflict state marking
the files that need manual conflict resolution.

After you have resolved the conflicts, you can continue the backport process by running:

cherry_picker --continue

If you don't have cherry-picker installed, see the installation guide.