Add breadboard diagrams for Exercises A and B #3

Create clear, original breadboard diagrams for the two LED-only lessons.

Acceptance criteria

• one diagram each for Exercises A and B
• diagrams match the maintained pin maps exactly
• each LED visibly has its own 220–330 Ω series resistor
• power rails, LED polarity, and ground are labeled
• source/editable format is committed alongside an exported SVG or PNG
• lesson pages embed the diagrams with descriptive alt text

Do not copy diagrams from another tutorial unless their license explicitly permits redistribution and attribution is included.