Fix: index document versions as their root document

The search index and the LLM index hold root documents only, a root being
indexed with its newest version's content. Every write path therefore had to
remember to hand them the root. Several did not: adding or deleting a note on
a version, restoring a trashed document together with its versions, and
reprocessing a version all wrote the version into the index under its own id,
where it could be returned as a separate search result. The paths that walk the
whole library did the same: the document_index reindex command put every
version in the search index, a full LLM index rebuild embedded every version,
and an incremental LLM update scoped to a version id indexed it under its own
id. Asking for documents like a version looked the version's own id up in the
index and silently found nothing.

WriteBatch.add_or_update, WriteBatch.add_or_update_ids and
llm_index_add_or_update_document now resolve a version to its root themselves.
The reindex command and update_llm_index only walk root documents, and an
incremental LLM update is scoped to the roots of the given ids through
versioning.root_document_ids, which add_or_update_ids shares. more_like_id
returns the root's id for a version. The reprocess task no longer picks the root
for the indexes and only still clears the caches of both documents.

src/documents/management/commands/document_index.py

@@ -67,18 +67,22 @@ class Command(PaperlessCommand):
                 if options.get("recreate"):
                     wipe_index(settings.INDEX_DIR)
 
-                documents = Document.objects.select_related(
-                    "correspondent",
-                    "document_type",
-                    "storage_path",
-                    "owner",
-                ).prefetch_related(
-                    "tags",
-                    "notes__user",
-                    "custom_fields__field",
-                    "versions",
-                    "barcodes",
-                    "versions__barcodes",
+                documents = (
+                    Document.objects.filter(root_document__isnull=True)
+                    .select_related(
+                        "correspondent",
+                        "document_type",
+                        "storage_path",
+                        "owner",
+                    )
+                    .prefetch_related(
+                        "tags",
+                        "notes__user",
+                        "custom_fields__field",
+                        "versions",
+                        "barcodes",
+                        "versions__barcodes",
+                    )
                 )
                 total = documents.count()
                 rebuild_kwargs = {}