phsl / new-api

- Introduce a global CSS utility `with-pastel-balls` in `web/src/index.css`, rendering pastel “blur balls” via ::before with CSS variables (`--pb1..--pb4`, `--pb-opacity`, `--pb-blur`) for easy theming.
- Apply the utility to pricing header cards and skeletons:
  - `web/src/components/table/model-pricing/layout/header/PricingVendorIntro.jsx`
  - `web/src/components/table/model-pricing/layout/header/PricingVendorIntroSkeleton.jsx`
- Remove per-component inline `linear-gradient(...)` backgrounds and redundant absolute-positioned decoration nodes to reduce duplication.
- Dark mode:
  - Keep the same pastel palette (pink/lavender/mint/peach).
  - Increase visibility with `--pb-opacity: 0.36`, `--pb-blur: 65px`, and `mix-blend-mode: screen`.
- No functional logic changes; UI-only. Lint passes.

Affected files:
- web/src/index.css
- web/src/components/table/model-pricing/layout/header/PricingVendorIntro.jsx
- web/src/components/table/model-pricing/layout/header/PricingVendorIntroSkeleton.jsx