chore: consolidate settings, enhance skill scripts, and reformat content

- Migrate settings from settings.local.json to settings.json with expanded permissions
- Add helper scripts (find_newsletter_number.sh, prepare_url.sh) to mt-add-post skill
- Update skill documentation and configuration
- Apply consistent formatting across config, content, and layout files
- Update workflow, gitignore, and netlify configuration

.gitattributes

@@ -0,0 +1,3 @@
+* text eol=crlf
+
+*.sh text eol=lf