test: rename SearchSpace -> Workspace across tests + fixtures (Phase 2 Wave F)

Apply the same rename to surfsense_backend/tests: workspace_id fields/vars,
Workspace* classes/schemas, table name searchspaces -> workspaces in raw SQL,
and the API URL spellings -> /workspaces. Preserves the carve-out wire literals
tests assert (Celery task names, OTel key "search_space.id").

surfsense_backend/tests/unit/notifications/api/test_transform.py

@@ -53,7 +53,7 @@ def _notification(**overrides) -> Notification:
     defaults = {
         "id": 1,
         "user_id": uuid.uuid4(),
-        "search_space_id": 3,
+        "workspace_id": 3,
         "type": "document_processing",
         "title": "Title",
         "message": "Message",

surfsense_backend/tests/unit/notifications/service/messages/test_document_processing.py

@@ -10,7 +10,7 @@ pytestmark = pytest.mark.unit
 
 
 def test_operation_id_encodes_type_and_space():
-    """The operation id embeds the document type and search space id."""
+    """The operation id embeds the document type and workspace id."""
     op = msg.operation_id("FILE", "report.pdf", 9)
     assert op.startswith("doc_FILE_9_")
 

surfsense_backend/tests/unit/notifications/service/messages/test_insufficient_credits.py

@@ -9,8 +9,8 @@ from app.notifications.service.messages import insufficient_credits as msg
 pytestmark = pytest.mark.unit
 
 
-def test_operation_id_encodes_search_space():
-    """The operation id embeds the search space id."""
+def test_operation_id_encodes_workspace():
+    """The operation id embeds the workspace id."""
     assert msg.operation_id("doc.pdf", 9).startswith("insufficient_credits_9_")