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/micromelon-code-editor-260.mdx

@@ -1,7 +1,7 @@
 ---
 title: "Micromelon Code Editor 2.6.0"
 date: "2022-08-01"
-categories: ["News & Updates", "All"]
+categories: ["News & Updates"]
 tags: []
 excerpt: "Micromelon Code Editor 2.6.0 was released on the 2nd August 2022 Here at Micromelon we are continually making changes and improvements to all our product lines, including hardware and software. Previously the best place to find out about these update"
 featuredImage: "/images/resources/micromelon-code-editor-260.png"
@@ -27,4 +27,4 @@ Once you’re done with all the tabs you’ve got open, you can easily close the
 
 ![](/images/content/71bc9a-screen-shot-2022-06-02-at-4.38.47-pm.png)
 
-And that’s it for now! To get the latest version, jump into the Code Editor and click File -> Check for Updates or on Mac click Micromelon IDE -> Check for updates.
+And that’s it for now! To get the latest version, jump into the Code Editor and click File -> Check for Updates or on Mac click Micromelon IDE -> Check for updates.