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/activity-servo-gauge.mdx

@@ -1,8 +1,10 @@
 ---
 title: "Activity: Servo Gauge"
 date: "2024-12-31"
-categories: ["Activities", "All", "Simulator Activities"]
+categories: ["Activities", "Simulator Activities"]
 tags: ["Attachments", "Servo Motors", "Intermediate"]
+codingSkills: []
+roverConcepts: ["Servo Motors"]
 excerpt: "Use a micro servo to make your own visual gauges. Program the gauge to react to a sensor value, motor speed, or robot tilt to visualise data in a new way. In this activity, we’ll be making a gauge to display the stability of the rover."
 featuredImage: "/images/resources/activity-servo-gauge.jpg"
 ---
@@ -67,8 +69,6 @@ For this activity, we will use the y-axis of the accelerometer as our sensor. Th
 
 Finally, place a ‘Move Servo’ block into the loop and put the scale function inside. Run the code and tilt the robot on its side. The gauge should move the hand the more you tilt the rover.
 
-![](/images/content/c89ca3-complete-code.png)
-
-**Tip:** 
+**Tip:**
 
 Try changing some of the colours on the scale and adding numbers to it. Maybe connect it to other sensors like the Ultrasonic, and use the gauge to display how close an object is to the rover.