feat: Add Step 7 Auto Alt-Text Generation to LocalGov Drupal walkthrough

Add new walkthrough step demonstrating the AI-powered auto alt-text
generation feature. This step shows how Amazon Nova vision model
automatically generates WCAG-compliant image descriptions when
uploading images to the Media Library.

Changes:
- Insert new step-7.njk for Auto Alt-Text Generation after step 6
- Rename existing steps 7-11 to 8-12 (PDF converter, DEMO banner,
  Listen to Page, Translate, Cleanup)
- Update totalSteps from 11 to 12 across all walkthrough files
- Add screenshots showing the feature in action
- Update walkthroughs.yaml with new step and 40-minute duration

Author: chrisns

src/_data/walkthroughs.yaml

@@ -5,10 +5,10 @@
 
 walkthroughs:
   localgov-drupal:
-    totalSteps: 11
+    totalSteps: 12
     url: "/walkthroughs/localgov-drupal/"
     title: "LocalGov Drupal Walkthrough"
-    duration: "37 minutes"
+    duration: "40 minutes"
     hasWalkthrough: true
     category: "cms"
     steps:
@@ -30,6 +30,9 @@ walkthroughs:
       - title: "Content simplified"
         description: "Simplify text to plain English with one click"
         time: "4 minutes"
+      - title: "Auto alt-text generated"
+        description: "See AI generate accessible image descriptions automatically"
+        time: "3 minutes"
       - title: "PDF converted to web"
         description: "Convert legacy PDFs to accessible web content"
         time: "4 minutes"

src/assets/images/walkthroughs/localgov-drupal/ai-features/alt-text-generated-desktop.png

@@ -2,8 +2,8 @@
 layout: layouts/walkthrough.njk
 title: "Walkthrough Complete - LocalGov Drupal"
 description: You've completed the LocalGov Drupal walkthrough
-currentStep: 9
-totalSteps: 8
+currentStep: 13
+totalSteps: 12
 scenarioId: localgov-drupal
 ---
 
@@ -106,7 +106,7 @@ scenarioId: localgov-drupal
 {# Story 15.3: Completion next steps with proper links #}
 {% set scenarioId = "localgov-drupal" %}
 {% set scenarioName = "LocalGov Drupal" %}
-{% set totalSteps = 8 %}
+{% set totalSteps = 12 %}
 {% include "components/completion-next-steps.njk" %}
 
 {# Story 2.10: Cleanup Instructions Component #}

src/assets/images/walkthroughs/localgov-drupal/ai-features/alt-text-upload-desktop.png

@@ -3,7 +3,7 @@ layout: layouts/walkthrough.njk
 title: LocalGov Drupal Walkthrough
 description: Step-by-step guide to exploring your deployed LocalGov Drupal CMS with AI features
 currentStep: 0
-totalSteps: 9
+totalSteps: 12
 scenarioId: localgov-drupal
 ---
 

src/walkthroughs/localgov-drupal/complete.njk

@@ -3,7 +3,7 @@ layout: layouts/walkthrough.njk
 title: "Step 1: Log in to Drupal - LocalGov Drupal Walkthrough"
 description: Get your credentials and access the Drupal admin dashboard
 currentStep: 1
-totalSteps: 11
+totalSteps: 12
 timeEstimate: "3 minutes"
 scenarioId: localgov-drupal
 ---