Chore: move mail parser sample files to paperless/tests/samples/mail/

Relocate all mail test fixtures from src/paperless_mail/tests/samples/ to
src/paperless/tests/samples/mail/ ahead of the parser plugin refactor.
Add the new path to the codespell skip list to prevent false-positive
spell corrections in binary/fixture email files.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pyproject.toml

@@ -256,7 +256,7 @@ lint.isort.force-single-line = true
 [tool.codespell]
 write-changes = true
 ignore-words-list = "criterias,afterall,valeu,ureue,equest,ure,assertIn,Oktober,commitish"
-skip = "src-ui/src/locale/*,src-ui/pnpm-lock.yaml,src-ui/e2e/*,src/paperless_mail/tests/samples/*,src/documents/tests/samples/*,*.po,*.json"
+skip = "src-ui/src/locale/*,src-ui/pnpm-lock.yaml,src-ui/e2e/*,src/paperless_mail/tests/samples/*,src/paperless/tests/samples/mail/*,src/documents/tests/samples/*,*.po,*.json"
 
 [tool.pytest]
 minversion = "9.0"