feat: speed up copy-flash timing by ~25%

Reduce active phase from 100ms to 75ms, fade transition from 300ms to
225ms, and cleanup delay from 350ms to 275ms for snappier feedback.

Refs #100

src/popup/styles/main.css

@@ -29,6 +29,6 @@ body {
 
 .copy-flash-fade {
     transition:
-        background-color 300ms ease-out,
-        color 300ms ease-out;
+        background-color 225ms ease-out,
+        color 225ms ease-out;
 }