New: Darkness & Warmth sliders, so "dark mode" isn't just one fixed shade

Hey everyone 👋

Since launch, the most common piece of feedback was that a single fixed "dark" wasn't dark enough for some people and too harsh for others. So instead of picking one shade for everyone, PDF Dark now has two independent sliders:

- Darkness (50-100%): lifts the background up toward white if full black feels too harsh on your eyes

- Warmth (0-100%): shifts the color temperature toward a warm, candle-light tone for night reading, similar to what f.lux / Night Shift do for your screen

Both apply live in the preview before you export, so you can dial in exactly the shade you actually want instead of being stuck with one default.

Still free, still no upload, still runs entirely in your browser. Would love to hear what settings people land on, especially if you read a lot at night.