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/windup-rover.mdx

@@ -3,6 +3,8 @@ title: "Activity: Wind-up Rover"
 date: "2021-06-03"
 categories: ["Activities", "All"]
 tags: ["Iteration", "Variables", "Accelerometer", "Motors", "Maths", "Intermediate"]
+codingSkills: ["Iteration", "Variables", "Maths"]
+roverConcepts: ["Accelerometer", "Motors"]
 excerpt: "Learn iteration, variables, maths, and how to use the Rover’s motors and accelerometer."
 featuredImage: "/images/resources/windup-rover.jpg"
 ---
@@ -10,53 +12,9 @@ featuredImage: "/images/resources/windup-rover.jpg"
 
 Create a classic wind up toy out of our rover. The rover records the number of seconds that it is held upside down and once placed right way up on a surface it will move forward. The longer the rover was held upside down the longer it will move forward and the faster it will go. For more interesting wind up rovers, incorporate the LEDs and Buzzers to also respond and change to the wind up time.
 
-####
-  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/Y-lzGxjS-og" title="Wind-up Rover Activity Demonstration" frameBorder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowFullScreen></iframe>
 
 ### Setup