fix(assessments): enable engine by default and wire into live UI

The assessment engine was built but opt-in and hidden: flag defaulted
off, no sidebar entry, and no settings toggle. Default assessments_engine
on, auto-seed catalog when empty, add Settings toggle and Assessments
nav, and surface guidance from the patients list.

tests/Feature/CareAssessmentApiTest.php

@@ -91,6 +91,7 @@ class CareAssessmentApiTest extends TestCase
 
     public function test_api_lists_templates_and_404_when_flag_off(): void
     {
+        // Engine defaults ON when rollout flag is unset.
         $this->getJson('/api/v1/assessment-templates')
             ->assertOk()
             ->assertJsonPath('data.0.code', fn ($c) => is_string($c));
@@ -100,6 +101,7 @@ class CareAssessmentApiTest extends TestCase
                 'rollout' => [CareFeatures::ASSESSMENTS_ENGINE => false],
             ]),
         ]);
+        $this->organization->refresh();
 
         $this->getJson('/api/v1/assessment-templates')->assertNotFound();
     }