Soft Gradient Backgrounds

Create 4 soft, blurred "mesh gradient" backgrounds as SVG files for my website's hero sections.

- Brand colour: #2563eb
- Mood: [e.g. calm and premium / festive and bright / dark and techy]

RULES
- Each SVG uses viewBox="0 0 1600 1000", a solid base colour and 3–4 large circles blurred with an feGaussianBlur filter (stdDeviation about 140), with preserveAspectRatio="xMidYMid slice"
- Build the palettes around my brand colour: 2 light and 2 dark versions, each with good contrast for a headline on top (tell me whether to use white or black text on each)
- Keep each file under 2 KB and use no raster images

OUTPUT
Each SVG in its own code block with a name, then a CSS example that uses one as a full-width hero background with text on top.