DEV: merge post-action-feedback CSS into common file (#34080)

Concerns this button feedback

<img width="190" height="152" alt="image"
src="https://github.com/user-attachments/assets/805a9258-2130-4e2e-99d4-50d9638c825b"
/>



This change is pretty straightforward, the desktop css includes all
styling for the `.post-action-feedback-alert`, so that can be simply
moved to common. The mobile alert was removed by
https://github.com/discourse/discourse/pull/31375 (because we open a
link modal instead)... so the mobile styles aren't actually applied
anywhere (no plugins either).

app/assets/stylesheets/common/post-action-feedback.scss

@@ -36,3 +36,42 @@
     }
   }
 }
+
+.post-action-feedback-alert {
+  position: absolute;
+  top: -1.5rem;
+  left: 60%;
+  transform: translateX(-50%);
+  color: var(--success);
+  padding: 0.25rem 0.5rem;
+  white-space: nowrap;
+  font-size: var(--font-down-2);
+  opacity: 0;
+  z-index: calc(z("timeline") + 1);
+}
+
+.--transition {
+  .post-action-feedback-alert,
+  .post-action-feedback-svg {
+    transition:
+      opacity 0.25s,
+      color 0.25s;
+  }
+}
+
+.--activated {
+  .post-action-feedback-alert,
+  .post-action-feedback-svg {
+    opacity: 1;
+  }
+
+  .post-action-feedback-alert {
+    &.-success {
+      color: var(--success);
+    }
+
+    &.-fail {
+      color: var(--danger);
+    }
+  }
+}

app/assets/stylesheets/desktop/_index.scss

@@ -2,7 +2,6 @@
 @import "latest-topic-list";
 @import "login-signup-page";
 @import "modal";
-@import "post-action-feedback";
 @import "topic";
 @import "topic-list";
 @import "topic-post";

app/assets/stylesheets/desktop/post-action-feedback.scss

@@ -1,38 +0,0 @@
-.post-action-feedback-alert {
-  position: absolute;
-  top: -1.5rem;
-  left: 60%;
-  transform: translateX(-50%);
-  color: var(--success);
-  padding: 0.25rem 0.5rem;
-  white-space: nowrap;
-  font-size: var(--font-down-2);
-  opacity: 0;
-  z-index: calc(z("timeline") + 1);
-}
-
-.--transition {
-  .post-action-feedback-alert,
-  .post-action-feedback-svg {
-    transition:
-      opacity 0.25s,
-      color 0.25s;
-  }
-}
-
-.--activated {
-  .post-action-feedback-alert,
-  .post-action-feedback-svg {
-    opacity: 1;
-  }
-
-  .post-action-feedback-alert {
-    &.-success {
-      color: var(--success);
-    }
-
-    &.-fail {
-      color: var(--danger);
-    }
-  }
-}

app/assets/stylesheets/mobile/_index.scss

@@ -1,6 +1,5 @@
 @import "login-signup-page";
 @import "modal";
-@import "post-action-feedback";
 @import "push-notifications-mobile";
 @import "topic-list";
 @import "topic-post";

app/assets/stylesheets/mobile/post-action-feedback.scss

@@ -1,39 +0,0 @@
-@keyframes d-toast-opening {
-  from {
-    transform: translateY(var(--transform-y, 10px));
-  }
-}
-
-.post-action-feedback-alert {
-  --transform-y: 0;
-  position: fixed;
-  top: calc(var(--header-offset) + 0.5rem);
-  left: 0;
-  right: 0;
-  margin-inline: 0.5rem;
-  z-index: z("max");
-  display: flex;
-  box-sizing: border-box;
-  padding: 1em 1.5em;
-  opacity: 1;
-  transition: opacity 0.5s;
-  border-radius: var(--d-border-radius);
-  color: var(--primary);
-  overflow: hidden;
-  background-color: var(--tertiary-very-low);
-  border: 1px solid var(--content-border-color);
-  box-shadow: var(--shadow-dropdown);
-  overflow-wrap: break-word;
-  animation: d-toast-opening 0.3s ease-in-out;
-  will-change: transform;
-
-  &.-fade-out {
-    opacity: 0;
-  }
-}
-
-@media (prefers-reduced-motion: no-preference) {
-  .post-action-feedback-alert {
-    --transform-y: 2vh;
-  }
-}