fix(admin): improve overview bar chart layout and alignment

backend/static/css/50-admin.css

@@ -197,7 +197,7 @@
 
 .bar-chart {
   display: flex;
-  align-items: flex-end;
+  align-items: stretch;
   gap: 0.4rem;
   height: 180px;
   margin-top: 1.25rem;
@@ -205,20 +205,27 @@
 }
 
 .bar-chart-col {
-  display: flex;
+  display: grid;
+  grid-template-rows: auto minmax(0, 1fr) auto;
   flex: 1;
   min-width: 0;
-  flex-direction: column;
   align-items: center;
-  justify-content: flex-end;
   gap: 0.35rem;
   height: 100%;
 }
 
-.bar-chart-bar {
+.bar-chart-track {
   width: 100%;
   max-width: 2.2rem;
-  min-height: 2px;
+  min-height: 0;
+  display: flex;
+  align-items: flex-end;
+  justify-content: center;
+}
+
+.bar-chart-bar {
+  width: 100%;
+  min-height: 0;
   border-radius: 6px 6px 0 0;
   background: linear-gradient(180deg, var(--primary, #8b5cf6), color-mix(in srgb, var(--primary, #8b5cf6) 55%, transparent));
 }