Migrate WordPress site to Hugo

Replaces the WordPress 7.0.2 / HitMag site with a static Hugo build,
deployed by Gitea Actions over rsync/SSH.

Content: 26 files (9 pages + 17 posts) as Markdown page bundles, plus
127 of 165 media attachments. The remaining 38 are media-library
leftovers that appear nowhere on the live site; they are listed in
MIGRATION.md.

The WXR export contains neither media binaries nor widgets, so both were
recovered from the live host before it is retired:
  - tools/fetch_media.py downloads all uploads, capping them at 2000px
  - tools/build_data.py scrapes the "Unsere Mitglieder" and
    "In Erinnerung" widgets into data/*.yaml

TablePress' six Termine tables became data/termine.yaml, rendered with
the newest year expanded and earlier years collapsed. Old permalinks are
not preserved (clean slugs, no redirects, as agreed).

Custom layouts, no third-party theme. Plain CSS, since the pinned Hugo
0.164.0 is the non-extended build and cannot compile Sass.

Verified: clean build with zero warnings, 718 internal links checked and
none broken, no surviving wp-content URLs.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

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