[STAGE 1] update 2025Q3 intro session link

[Nadin-Nov]

update YouTube link for 2025Q3 introductory session

🤔 This is a ...

• 🌟 New task
• 🌐 New module
• ⚙️ Update to an existing task
• 🔧 Update to an existing module
• 🔗 Update or addition of external resources or links
• 🐛 Fix in a task or related content
• 🛠 Fix in a module or related content
• ✏️ Fixed a typo or grammatical error
• 🔗 Fixed a broken link
• ❓ Other (specify: ****____****)

Checklist

• ✅ I have performed a self-review of my own code.
• 📝 I have commented my code, particularly in hard-to-understand areas.
• 🔧 I have made corresponding changes to the documentation (if applicable).
• 🚫 My changes generate no new warnings or errors.