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/survey-bot.mdx

@@ -3,6 +3,8 @@ title: "Activity: Survey Bot"
 date: "2021-06-03"
 categories: ["Activities", "All"]
 tags: ["Iteration", "IR", "Motors", "Maths", "Advanced", "Colour Sensors"]
+codingSkills: ["Iteration", "Maths"]
+roverConcepts: ["IR", "Motors", "Colour"]
 excerpt: "Learn iteration while using the IR sensors."
 featuredImage: "/images/resources/survey-bot.png"
 ---
@@ -10,53 +12,9 @@ featuredImage: "/images/resources/survey-bot.png"
 
 Program the rover to perform a distance survey of the area around it. Have the rover turn on the spot and print out the value of one of the IR distance sensors at intervals around the circle.
 
-####
-  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/8NlM1vmVNhQ" title="Survey Bot Activity Demonstration" frameBorder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowFullScreen></iframe>
 
 ### Setup