fix(tests): apply user edits when creating test from template

The form captured name/description/platform/procedure/tool edits but
never sent them — the created test always used the raw template values.

- TestTemplateInstantiate schema: add optional override fields
  (name, description, platform, procedure_text, tool_used)
- create_test_from_template service: accept *_override kwargs;
  use override value when provided, fall back to template value
- Router: pass all override fields from payload to service
- Frontend API createTestFromTemplate: accept overrides object, spread into body
- TestFromTemplateForm: pass all form state values as overrides

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

backend/app/routers/tests.py

@@ -185,6 +185,11 @@ def create_test_from_template(
             template_id=payload.template_id,
             technique_id_or_mitre=payload.technique_id,
             creator_id=current_user.id,
+            name_override=payload.name,
+            description_override=payload.description,
+            platform_override=payload.platform,
+            procedure_text_override=payload.procedure_text,
+            tool_used_override=payload.tool_used,
         )
         log_action(
             db,