🔧 Point repo metadata at Gitea; drop redundant .npmignore

The repository.url shipped github.com/tmueller/... but the real remote
is gitea.e1nsnull.de/tmu/..., so the npm page's Repository link 404'd.
Add homepage + bugs, fix the URL, and rename the CONTRIBUTING "GitHub"
reference to the forge. Delete .npmignore: when a package.json `files`
allowlist is present npm never consults .npmignore, so it was dead
weight that would only drift. Add "gitea" to the cspell dictionary.

CONTRIBUTING.md

@@ -81,7 +81,7 @@ Publishing is CI-only by policy. Local `npm publish` is not supported.
     ```sh
     npm version <patch|minor|major>
     ```
-4. Push the tag to GitHub:
+4. Push the tag to the forge (Gitea):
     ```sh
     git push --follow-tags origin main
     ```