Fix: consolidate and extend unicode NFC normalization for filenames and matching

Consolidates the scattered unicodedata.normalize("NFC", ...) calls introduced
by my earlier filename/path normalization work into a single
documents.utils.normalize_unicode() helper, and closes several gaps where
NFD-normalized filenames could still slip through unnormalized:

- Document.get_public_filename() now normalizes, fixing exported filenames
  built from an NFD title/correspondent name (the default, non-format export
  path was not covered by the earlier fix).
- DocumentViewSet.update_version() now normalizes the uploaded filename,
  matching PostDocumentView's existing behavior.
- ConsumerPlugin normalizes self.filename once at consumption time, covering
  the title fallback and Document.original_filename for every document
  source (consume folder, mail, API, barcode splits).
- Workflow trigger and mail rule filename/path matching (documents/matching.py,
  paperless_mail/mail.py) now normalize the document/attachment side before
  comparing, so an NFD filename matches an NFC-typed filter pattern instead of
  silently failing to match.
- WorkflowTriggerSerializer and MailRuleSerializer normalize filter_filename/
  filter_path and the attachment include/exclude patterns once at write time,
  so the read side isn't re-normalizing an already-canonical value on every
  match.

src/documents/tests/test_api_update_version_nfc.py

@@ -0,0 +1,69 @@
+import unicodedata
+from typing import TYPE_CHECKING
+from unittest import mock
+
+import celery.result
+import pytest
+from django.core.files.uploadedfile import SimpleUploadedFile
+
+from documents.models import Document
+
+if TYPE_CHECKING:
+    from documents.data_models import ConsumableDocument
+
+
+@pytest.fixture()
+def consume_file_mock():
+    with mock.patch("documents.tasks.consume_file.apply_async") as m:
+        m.return_value = celery.result.AsyncResult(id="test-task-id")
+        yield m
+
+
+@pytest.fixture()
+def directories(tmp_path, settings, _media_settings):
+    scratch = tmp_path / "scratch"
+    scratch.mkdir()
+    settings.SCRATCH_DIR = scratch
+    return scratch
+
+
+@pytest.mark.django_db
+class TestUpdateVersionNFCNormalization:
+    def test_nfd_filename_normalized_to_nfc(
+        self,
+        admin_client,
+        consume_file_mock: mock.MagicMock,
+        directories,
+    ):
+        """Uploaded new-version file with NFD filename must have its temp name stored as NFC."""
+        document = Document.objects.create(
+            title="Test",
+            content="content",
+            checksum="checksum",
+            mime_type="application/pdf",
+        )
+
+        nfd = unicodedata.normalize("NFD", "Rechnung März.pdf")
+        nfc = unicodedata.normalize("NFC", "Rechnung März.pdf")
+
+        assert nfd != nfc
+
+        uploaded = SimpleUploadedFile(
+            nfd,
+            b"%PDF-1.4 test",
+            content_type="application/pdf",
+        )
+        response = admin_client.post(
+            f"/api/documents/{document.pk}/update_version/",
+            {"document": uploaded},
+        )
+
+        assert response.status_code == 200
+
+        task_kwargs = consume_file_mock.call_args.kwargs["kwargs"]
+        input_doc: ConsumableDocument = task_kwargs["input_doc"]
+
+        assert input_doc.original_file.name == nfc, (
+            f"Expected NFC filename {nfc!r}, got {input_doc.original_file.name!r}"
+        )
+        assert unicodedata.is_normalized("NFC", input_doc.original_file.name)