Adopt shared WebUI structural primitives

webui/src/styles/postbox.css

@@ -52,7 +52,6 @@
   background: var(--panel-soft);
 }
 
-.postbox-bar,
 .postbox-bar-title,
 .postbox-icon-actions,
 .postbox-scope-row,
@@ -68,16 +67,6 @@
   align-items: center;
 }
 
-.postbox-bar {
-  flex: 0 0 auto;
-  min-height: 54px;
-  justify-content: space-between;
-  gap: 10px;
-  border-bottom: var(--border-line);
-  background: var(--panel-header);
-  padding: 8px 12px;
-}
-
 .postbox-bar-title {
   min-width: 0;
   gap: 8px;
@@ -95,18 +84,6 @@
   gap: 5px;
 }
 
-.postbox-total {
-  min-width: 24px;
-  height: 22px;
-  display: inline-grid;
-  place-items: center;
-  border-radius: 999px;
-  background: var(--line);
-  color: var(--text-strong);
-  font-size: 12px;
-  font-weight: 800;
-}
-
 .postbox-scope-control {
   flex: 0 0 auto;
   border-bottom: var(--border-line);
@@ -152,9 +129,7 @@
 }
 
 .postbox-search-row {
-  display: flex;
-  align-items: center;
-  gap: 5px;
+  width: 100%;
 }
 
 .postbox-search-row input {
@@ -383,27 +358,6 @@
   line-height: 1.4;
 }
 
-.postbox-empty {
-  min-height: 100%;
-  display: grid;
-  place-items: center;
-  align-content: center;
-  gap: 7px;
-  padding: 30px;
-  color: var(--muted);
-  text-align: center;
-}
-
-.postbox-empty.compact {
-  min-height: 180px;
-  padding: 20px;
-}
-
-.postbox-empty strong {
-  color: var(--text-strong);
-}
-
-.postbox-empty p,
 .postbox-note {
   max-width: 470px;
   margin: 0;