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/everything-to-know-about-3d-printing.mdx

@@ -1,7 +1,7 @@
 ---
 title: "A Crash Course on 3D Printing in the Classroom"
 date: "2022-08-03"
-categories: ["All"]
+categories: []
 tags: ["3D Printing"]
 excerpt: "Learn the fundamentals of 3D printing as a technology you can use in the classroom!"
 featuredImage: "/images/resources/everything-to-know-about-3d-printing.jpeg"
@@ -163,7 +163,6 @@ Finally, 3D printers have allowed people to make entire businesses based on cust
 
 So that is a crash course on 3D Printing. There is lots of content we purposely didn’t include in this blog post because it could honestly be a whole book. Things like which 3D Printers are best for classrooms, where I download models from, how I store my filament and how do I manage 30 or more students all wanting to print their new design at once are all great questions and ones that are best handled in a video call or meeting with some of our 3D printing experts at Micromelon. If this is you feel free to reach out via our contact form and we’ll be more than happy to support you on your 3D Printing journey.[Contact Us!](/contact)
 
-![](/images/content/15d396-black-spacer.png)
 
 ![](/images/content/6b505b-2021-12-16_16-01-19_1639630906.jpg-2_9aae3875-8e0b-41ff-8d46-14a38ce51916.webp.jpeg)