Site audit: fix broken images, add activity metadata, clean up content

- Remove broken image references from 25 MDX files (deleted spacer/content images)
- Add codingSkills and roverConcepts frontmatter to 24 activity pages
- Fix "Activity Demonstration" headings in 15 activity files (plain text -> h3)
- Remove unused "All" category from 89 MDX files
- Decode HTML entities (> <  ) in 9 content files
- Escape bare < > characters in MDX to fix build errors
- Standardize contact email to contact@micromelon.com.au
- Add missing description to rover-repair-request metadata
- Include previous session work: about-us updates, difficulty filtering,
  LearningPathway component, expanded schools list, new product/resource images

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

content/resources/build-guide-forklift.mdx

@@ -24,43 +24,36 @@ Click on the a button below to collect the print files!
 [Makerworld](https://makerworld.com/en/models/147782?from=search)
 
 
-![](/images/content/7e43d1-spacer.png)
 
 ## Step 1:
 
 ![](/images/content/0d9862-slide2.png)
 
-![](/images/content/3ec236-spacer.png)
 
 ## Step 2:
 
 ![](/images/content/1b8abb-slide3.png)
 
-![](/images/content/e984ed-spacer.png)
 
 ## Step 3:
 
 ![](/images/content/42c147-slide4.png)
 
-![](/images/content/548eac-spacer.png)
 
 ## Step 4:
 
 ![](/images/content/92d879-slide5.png)
 
-![](/images/content/88dbeb-spacer.png)
 
 ## Step 5:
 
 ![](/images/content/3c5543-slide6.png)
 
-![](/images/content/42bcf6-spacer.png)
 
 ## Complete
 
 ![](/images/content/62a624-complete.png)
 
-![](/images/content/b766e9-black-spacer.png)
 
 ## What’s Next?