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/flip-bot.mdx

@@ -3,6 +3,8 @@ title: "Activity: Flip Bot"
 date: "2021-06-03"
 categories: ["Activities", "All"]
 tags: ["Branching", "Iteration", "Accelerometer", "Motors", "Intermediate"]
+codingSkills: ["Branching", "Iteration"]
+roverConcepts: ["Accelerometer", "Motors"]
 excerpt: "Learn branching, iteration, and how to use the accelerometer."
 featuredImage: "/images/resources/flip-bot.png"
 ---
@@ -10,53 +12,9 @@ featuredImage: "/images/resources/flip-bot.png"
 
 Program the rover to flip itself upside down and then stop. There are many solutions to this problem. The rover must flip itself without being touched while running and once it has flipped it should stop. You could try combining this with the Turn Over Rover program to include lights.
 
-####
-  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/176tJNx-Kd8" title="Flip Bot Activity Demonstration" frameBorder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowFullScreen></iframe>
 
 ### Setup