feat: Add CSS styles for SidePanel component

frontend/src/components/SidePanel.css

@@ -0,0 +1,95 @@
+.side-panel {
+  display: flex;
+  flex-direction: column;
+  background-color: var(--surface);
+  border-left: var(--border-width) solid var(--border);
+  width: 300px;
+  height: 100%;
+}
+
+.panel-tabs {
+  display: flex;
+  flex-direction: column;
+  padding: var(--spacing-sm) 0;
+  background-color: var(--surface);
+  border-bottom: var(--border-width) solid var(--border);
+}
+
+.panel-tab {
+  display: flex;
+  align-items: center;
+  padding: var(--spacing-md);
+  background: transparent;
+  border: none;
+  border-radius: var(--border-radius);
+  cursor: pointer;
+  color: var(--text);
+  font-family: var(--font-family);
+  font-size: var(--font-size-md);
+  transition: background-color var(--transition-normal);
+  text-align: left;
+}
+
+.panel-tab:hover {
+  background-color: var(--hover);
+}
+
+.panel-tab.active {
+  background-color: var(--primary);
+  color: var(--background);
+}
+
+.tab-icon {
+  margin-right: var(--spacing-md);
+  font-size: var(--font-size-lg);
+}
+
+.tab-label {
+  font-weight: var(--font-weight-medium);
+}
+
+.panel-content-container {
+  flex: 1;
+  overflow-y: auto;
+  padding: var(--spacing-md);
+}
+
+.panel-content {
+  color: var(--text);
+  font-family: var(--font-family);
+  font-size: var(--font-size-md);
+}
+
+/* Responsive design */
+@media (max-width: 1024px) {
+  .side-panel {
+    width: 250px;
+  }
+}
+
+@media (max-width: 768px) {
+  .side-panel {
+    width: 100%;
+    height: 300px;
+    border-left: none;
+    border-top: var(--border-width) solid var(--border);
+  }
+  
+  .panel-tabs {
+    flex-direction: row;
+    overflow-x: auto;
+  }
+  
+  .panel-tab {
+    flex: 1;
+    justify-content: center;
+  }
+  
+  .tab-label {
+    display: none;
+  }
+  
+  .tab-icon {
+    margin-right: 0;
+  }
+}