feat: add mention notification creation and user search endpoints across multiple routers

devplacepy/static/css/messages.css

@@ -18,12 +18,43 @@
 .messages-list-header {
     padding: 1rem;
     border-bottom: 1px solid var(--border);
+    position: relative;
 }
 
 .messages-list-header input {
     font-size: 0.8125rem;
 }
 
+.search-dropdown {
+    display: none;
+    position: absolute;
+    top: 100%;
+    left: 0;
+    right: 0;
+    background: var(--bg-secondary);
+    border: 1px solid var(--border);
+    border-top: none;
+    border-radius: 0 0 var(--radius) var(--radius);
+    z-index: 100;
+    max-height: 240px;
+    overflow-y: auto;
+}
+
+.search-dropdown-item {
+    display: flex;
+    align-items: center;
+    gap: 0.625rem;
+    padding: 0.625rem 1rem;
+    font-size: 0.875rem;
+    color: var(--text-primary);
+    transition: background 0.15s;
+    text-decoration: none;
+}
+
+.search-dropdown-item:hover {
+    background: var(--bg-card-hover);
+}
+
 .messages-conversations {
     flex: 1;
     overflow-y: auto;
@@ -96,6 +127,7 @@
     flex: 1;
     overflow-y: auto;
     padding: 1rem;
+    padding-bottom: 0.5rem;
     display: flex;
     flex-direction: column;
     gap: 0.75rem;