Pink Noise GeneratorGenerate pink noise for balanced sound masking and relaxation.

Pink noise (1/f noise) is generated using the Voss-McCartney algorithm, which efficiently produces pink noise by summing multiple random number generators updated at different rates. The algorithm uses a set of octave-band generators: generator k updates every 2^k samples and adds a new random value. The sum of all generators produces an approximation of 1/f spectral distribution. Alternatively, a Kellet filter approach applies a series of first-order IIR filters to white noise: using three cascaded filters with coefficients (0.99886, 0.99332, 0.96900) to shape the spectrum. The result has a power spectral density of 1/f (-3 dB/octave). A 2-second buffer is filled and looped via AudioBufferSourceNode. Volume control uses a GainNode. The timer uses scheduled gain ramp for fadeout.