fix: #3613856 Remove the superseded stand-in posts and their orphaned tags

Issue: https://www.drupal.org/project/horizonaid/issues/3613856

Follow-up to the full Resources demo content merged in !12 (merged).

The twenty-six-post set replaces three earlier stand-in posts that carry the same three titles, but both sets shipped, so a fresh install imports 29 blog posts with three duplicate titles — visible in the Resources listing, in its pager count and in the Latest Updates slider on Home.

Their three tags (Health, Agriculture, Human rights) go with them: no post in the full set references them, and neither does any config or Canvas page, so they import as empty terms that appear in the Resources theme filter with nothing behind them.

Verified on a local install: blog nodes 29 → 26, /resources reports Shown articles: 1–9 of 26 over a three-page pager, and the theme filter lists only the three real themes.

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