Chore: Move the four duplicated parser sample PDFs into a shared paperless_testing location

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/paperless_testing/samples.py

@@ -0,0 +1,14 @@
+"""Test sample files that more than one app's tests need.
+
+A sample used by a single app stays in that app's ``tests/samples`` tree.
+Only a file that two or more apps need lives here, exactly once.
+"""
+
+from pathlib import Path
+
+SHARED_SAMPLES_DIR = (Path(__file__).parent / "sample_files").resolve()
+
+SIMPLE_DIGITAL_PDF = SHARED_SAMPLES_DIR / "simple-digital.pdf"
+MULTI_PAGE_DIGITAL_PDF = SHARED_SAMPLES_DIR / "multi-page-digital.pdf"
+WITH_FORM_PDF = SHARED_SAMPLES_DIR / "with-form.pdf"
+MULTI_PAGE_IMAGES_PDF = SHARED_SAMPLES_DIR / "multi-page-images.pdf"