Use proper border rather than shadow-border class

frontend/src/components/ThreadDisplayPlaceholder.vue

@@ -33,7 +33,7 @@
 		margin-bottom: 1rem;
 		transition: background-color 0.2s;
 		position: relative;
-		@extend .shadow_border;
+		border: thin solid $color__gray--darker;
 
 		@at-root #{&}__bar {
 			@include flash;

frontend/src/components/routes/Settings.vue

@@ -80,7 +80,7 @@
 
 	.settings_menu {
 		width: 15rem;
-		@extend .shadow_border;
+		border: thin solid $color__gray--darker;
 		background-color: #fff;
 		padding: 1rem;
 		border-radius: 0.25rem;
@@ -102,7 +102,6 @@
 			cursor: pointer;
 			position: relative;
 			border-radius: 0.25rem;
-			color: $color__text--secondary;
 
 			&:first-child { margin-top: 0.5rem; }
 			&:last-child { margin-bottom: 0.5rem; }
@@ -150,7 +149,7 @@
 		background-color: #fff;
 		border-radius: 0.25rem;
 		margin-left: 2rem;
-		@extend .shadow_border;
+		border: thin solid $color__gray--darker;
 	}
 
 	@media (max-width: 420px) {

frontend/src/components/routes/SettingsGeneral.vue

@@ -260,8 +260,8 @@
 		padding: 1rem;
 		transition: all 0.2s;
 
-		@at-root #{&}--picture.dragging {
-			//background-color: $color__lightgray--primary;
+		@at-root #{&}--picture .dragging {
+			background-color: $color__lightgray--primary;
 		}
 
 		@at-root #{&}__overlay {

frontend/src/components/routes/ThreadNew.vue

@@ -276,7 +276,7 @@
 
 	.thread_meta_info {
 		background-color: #fff;
-		@extend .shadow_border;
+		border: thin solid $color__gray--darker;
 		border-radius: 0.25rem;
 		padding: 1rem;
 		margin: 1rem 0;
@@ -338,12 +338,12 @@
 		display: flex;
 		background-color: #fff;
 		border-radius: 0.25rem;
-		box-shadow: 0 0 0.3rem rgba(175, 175, 175, 0.5);
+		border: thin solid $color__gray--darker;
 
 		transition: all 0.2s;
 
 		@at-root #{&}--focus {
-			box-shadow: 0 0 0.3rem rgba(175, 175, 175, 1);
+			border: thin solid $color__gray--darkest;
 		}
 
 		@at-root #{&}__format_bar {