Fix postcode search layout and placeholder styling

- Keep postcode controls on one line (flex-wrap: nowrap)
- Remove uppercase transform from placeholder text
- Update placeholder to "Enter postcode..." for consistency

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/styles.css

@@ -320,7 +320,7 @@ body {
     gap: 0.75rem;
     align-items: center;
     justify-content: center;
-    flex-wrap: wrap;
+    flex-wrap: nowrap;
 }
 
 .postcode-input {
@@ -328,7 +328,10 @@ body {
     max-width: 180px;
     padding: 0.6rem 1rem;
     font-size: 0.95rem;
-    text-transform: uppercase;
+}
+
+.postcode-input::placeholder {
+    text-transform: none;
 }
 
 .radius-select {