feat(gallery): add reference batch R01-R04 modeled on period hardware

I built four widgets as inline SVG (the substrate that ports to svg.el), modeled on 1950s-60s lab and console hardware from the reference photos now filed in the catalogue's working directory:

- R01 moving-coil VU meter: cream face, authentic nonlinear dB arc (-20 to +3), red zone, ballistic needle on the live signal.
- R02 calibrated vernier dial: rotating tick-ring disc with radial numerals under a fixed hairline, fluted bakelite knob, reads to a tenth.
- R03 bat-handle toggle: chrome lever on a hex bushing, snaps ON/OFF with lit legends.
- R04 bakelite fluted knob: scalloped skirt, glossy dome, amber index over a printed 0-10 scale.

I verified all four in headless Chrome: the VU animates with ballistics, the dial and knob track drags, the toggle throws, no console exceptions. The gallery now carries 57 cards.

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