feat(gallery): add R14 spade-pointer knob and R15 multi-band dial

Two radio-receiver widgets as inline SVG, after a 1920s GE receiver panel and a Hallicrafters shortwave dial pair:

- R14 spade-pointer tuning knob: a knurled bakelite knob carries a bright spade pointer over a 0-10 scale rendered as engraved relief (each mark drawn with a light offset twin, ink-free like the source panel). The knurl ring turns with the knob.
- R15 multi-band dial: four nested band arcs on a cream face read by one long needle; the active ring draws bold and the rest fade. Dragging the main dial tunes within the active band's frequency range, and clicking the bandspread dial steps bands, turning its own needle.

I verified both in headless Chrome: the spade knob tracks drags, tuning moves the needle and readout, the band click switches range and re-weights the rings, no console exceptions. The gallery is at 68 cards.

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