Transistor Stage 0, one zone (GF / D3)

PN2222 low-side switch · clone ×4 for the other pins · Arduino Uno R3

+5V rail GND rail Uno 5V D3 D2 GND 1kΩ Q1 PN2222 B C E → GND LED warm white anode + 220Ω BTN D2 → button → GND current: +5V → LED → 220Ω → collector → (Q1) → emitter → GND
+5V GND / wire signal (PWM) LED
Then clone the transistor block ×4, same wiring, just change the Arduino pin:
ZoneArduino pin → 1kΩ → baseFixtures
GF_INTD3living + kitchen ceilings
UP_INTD5bedrooms + attic
EXTD6porch, entry, deck, balcony
FIRED9hearth (flicker)

Each zone shares the same +5V and GND rails. Add more LEDs to a zone by putting each one (anode→+5V, cathode→220Ω→collector) in parallel on that transistor.

PN2222 leg order, flat face toward you, legs down: E · B · C (left→right). If nothing lights, swap E↔C, that's the usual culprit and it's harmless.