chore(linting): refresh configs and sweep auto-fix

Pull in the refreshed linter and tooling configs (editorconfig,
gitignore, gitattributes, prettierignore, prettierrc, markdownlint,
yamllint, env.example, dotnet-tools) and run prettier and markdownlint
in --fix / --write mode across the repo so the existing tree matches
the new rules.

- prettier 2-space indent on yaml/yml and json overrides, asterisk
  strong, underscore emphasis, proseWrap always
- markdownlint MD007 indent aligned to 2 and MD049 to underscore so
  prettier output stays passing
- preflight Block F also ignores CLAUDE.md (gitignored personal file)
- prettierignore extended to keep HellionChat.yaml manifest and the
  NuGet packages.lock.json out of the formatter

No semantic content changed; csharpier, build, full build-suite
(729/729) and the new prettier/markdownlint/yamllint checks all green.

.github/ISSUE_TEMPLATE/config.yml

@@ -1,15 +1,15 @@
 blank_issues_enabled: false
 
 contact_links:
-    - name: Security vulnerability
-      url: mailto:kontakt@hellion-media.de?subject=%5BHellionChat%20Security%5D
-      about: Do not open a public issue for security problems. Report by e-mail instead.
+  - name: Security vulnerability
+    url: mailto:kontakt@hellion-media.de?subject=%5BHellionChat%20Security%5D
+    about: Do not open a public issue for security problems. Report by e-mail instead.
 
-    - name: Upstream Chat 2 issue
-      url: https://github.com/Infiziert90/ChatTwo/issues
-      about:
-          If the issue exists in upstream Chat 2 too, please report it there so the original maintainers see it as well.
+  - name: Upstream Chat 2 issue
+    url: https://github.com/Infiziert90/ChatTwo/issues
+    about:
+      If the issue exists in upstream Chat 2 too, please report it there so the original maintainers see it as well.
 
-    - name: Discord
-      url: https://discord.com/users/j.j_kazama
-      about: Quick questions, casual feedback. Bug reports still go through the issue tracker for tracking.
+  - name: Discord
+    url: https://discord.com/users/j.j_kazama
+    about: Quick questions, casual feedback. Bug reports still go through the issue tracker for tracking.