fix: nav bar layout - reduce gaps and improve responsive

- Reduced gaps in nav-left, nav-center, nav-right
- Removed absolute positioning on nav-center
- Added flex-wrap and flex-shrink for responsive behavior

Author: ThanhNguyxn

src/index.css

@@ -51,22 +51,25 @@ body {
 .nav-left {
   display: flex;
   align-items: center;
-  gap: 1rem;
+  gap: 0.5rem;
+  flex-shrink: 0;
 }
 
 .nav-center {
   display: flex;
   align-items: center;
-  gap: 0.5rem;
-  position: absolute;
-  left: 50%;
-  transform: translateX(-50%);
+  gap: 0.25rem;
+  flex-wrap: wrap;
+  justify-content: center;
+  flex: 1;
+  margin: 0 0.5rem;
 }
 
 .nav-right {
   display: flex;
   align-items: center;
-  gap: 1rem;
+  gap: 0.375rem;
+  flex-shrink: 0;
 }
 
 /* Tab Buttons */