Raspberry Pi Pico 3-Burst Police Flip-Flop (2 LED GP11 + GP12)

Rhythmic variation of the police strobe project — 3-burst flip-flop! 🚨 Same 2 LED circuit as #151 (GP11 red + GP12 blue), but different pattern: red LED flashes 3 times rapidly, then blue flashes 3 times, forever. This "burst + switch" pattern is the most recognizable rhythm of real police siren lights. Learn parametrized function `def burst(led, count, duration_ms)`, rhythm design, and generating different visual effects with code on same circuit.