Consistent hero layouts, activity page redesign, new content, and YouTube embeds

- Product pages (Code Editor, Robot Simulator): text-left/image-right hero layout
- Related resources capped at 3 items on all product pages
- Making Music activities renamed to I, II, III
- New Maze I/II/III and Sumo I/II/III difficulty-graded activities
- YouTube demo videos restored on 12 activity pages from old site
- Activity pages: two-column hero with coding skills & rover concepts tags
- Blog/news pages: same two-column hero layout with date
- Resource type extended with codingSkills, roverConcepts, tags fields
- Removed raw "Relevant Coding Skills/Rover Concepts" text from activity MDX

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

content/resources/turn-over-rover.mdx

@@ -3,6 +3,8 @@ title: "Activity: Turn Over Rover"
 date: "2021-06-03"
 categories: ["Activities", "All"]
 tags: ["Branching", "Iteration", "Accelerometer", "LEDs", "Beginner"]
+codingSkills: ["Branching", "Iteration"]
+roverConcepts: ["Accelerometer", "LEDs"]
 excerpt: "Learn branching, iteration, and how to use the accelerometer and LEDs."
 featuredImage: "/images/resources/turn-over-rover.png"
 ---
@@ -10,53 +12,9 @@ featuredImage: "/images/resources/turn-over-rover.png"
 
 Program the rover to detect if it is upside down or not. When the rover is the right way up set it's LEDs to green. When the rover is upside down set the LEDs to red. The rover should change the LEDs as soon as it detects a change in orientation, you should not need to press the play button to trigger a change in colour.
 
-####
-  Relevant Coding Skills
+### Activity Demonstration
 
-    Branching
-
-    Iteration
-
-    Functions
-
-    Variables
-
-	-->
-
-    Algorithm Design
-
-  -->
-
-    Maths
-
-####
-   Relevant Rover Concepts
-
-    Ultrasonic
-
- -->
-
-    IR
-
-	 -->
-
-    Colour
-
-    Gyroscope
-
-    Accelerometer
-
-    Motors
-
- -->
-
-    LEDs
-
-    Buzzer
-
- 	-->
-
-Activity Demonstration
+<iframe width="560" height="315" src="https://www.youtube.com/embed/34mfI0SsaOs" title="Turn Over Rover Activity Demonstration" frameBorder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowFullScreen></iframe>
 
 ### Setup