fix: keep reaction icons evenly distributed when Share is disabled

The reaction row gave every item except the last a `Modifier.weight()`,
which made the last item collapse to its natural width and hug the right
edge of the content area. With Share (icon-only) as the default last
item, all icons appeared evenly distributed.

When the user disabled Share, the last weighted slot moved to Zap. Zap
renders icon + counter, so its natural-width row took more space at the
right and pulled the rightmost icon away from where the other icons sat
(each at the left of a now-wider weighted slice), leaving the row
looking unbalanced.

Give every reaction an equal weighted slice so icons sit at the left of
their slice regardless of which reactions are enabled. The unused space
at the end of the last slice naturally provides the right-side padding
where Share used to sit.

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/ReactionsRow.kt

@@ -387,7 +387,6 @@ private fun GenericInnerReactionRow(
     renderReaction: @Composable (ReactionRowItem) -> Unit,
 ) {
     val enabledReactions = remember(reactions) { reactions.filter { it.enabled } }
-    val lastIndex = enabledReactions.lastIndex
 
     Row(
         verticalAlignment = CenterVertically,
@@ -403,14 +402,12 @@ private fun GenericInnerReactionRow(
             }
         }
 
-        enabledReactions.forEachIndexed { index, item ->
-            val isLast = index == lastIndex
+        enabledReactions.forEach { item ->
             val itemWeight = if (item.action == ReactionRowAction.Reply) weightTwo else 1f
-            val mod = if (isLast) Modifier else Modifier.weight(itemWeight)
             Row(
                 verticalAlignment = CenterVertically,
                 horizontalArrangement = RowColSpacing,
-                modifier = mod,
+                modifier = Modifier.weight(itemWeight),
             ) {
                 renderReaction(item)
             }