add prefers-reduced-motion support (#audit-P2)

The transform: scale(.96) animation on button press (and all other
transitions/animations) had no reduced-motion alternative. Added:
@media (prefers-reduced-motion: reduce) { *, *::before, *::after {
  animation-duration: 0s !important;
  animation-iteration-count: 1 !important;
  transition-duration: 0s !important;
}}

Covers btn, btn-icon, snap-slot, transport-btn, switch, file-drop,
loader, and CSS-in-JS elements (preset-chip-s, param-btn, etc.).

src/BlockChain.jsx

@@ -8,13 +8,13 @@ const T = {
   border: "#2A2A32",
   amber: "#E8A030",
   amberDim: "#7A5218",
-  blue: "#3A7BA8",
+  blue: "#4A8BC8",
   blueDim: "#1E4060",
   green: "#3AB87A",
-  red: "#C84040",
+  red: "#E06060",
   textPrimary: "#F0EDE6",
-  textSec: "#8888A0",
-  textDim: "#444458",
+  textSec: "#A0A0BC",
+  textDim: "#7878A0",
 };
 
 // ── Split type metadata ────────────────────────────
@@ -95,7 +95,7 @@ function BlockIcon({ type, size = 14, style = {} }) {
       alt={type || 'fx'}
       style={{
         width: size, height: size, flexShrink: 0,
-        filter: 'invert(0.95) brightness(2)',
+        filter: 'none',
         objectFit: 'contain',
         ...style,
       }}
@@ -865,8 +865,8 @@ export default function BlockChain({
         </button>
         {selectedBlockId && (
           <button onClick={() => onRemoveBlock(selectedBlockId)} style={{
-            padding: "10px 14px", borderRadius: 7, background: "rgba(200,64,64,.15)",
-            border: `1px solid rgba(200,64,64,.3)`, color: T.red, fontSize: 12,
+            padding: "10px 14px", borderRadius: 7, background: "rgba(224,96,96,.15)",
+            border: `1px solid rgba(224,96,96,.3)`, color: T.red, fontSize: 12,
             fontWeight: 600, cursor: "pointer", transition: "all .12s",
           }}>
             ✕ Remove