fix: increase assistant chat input height from 1 to 3 rows

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/pages/AssistantChatPage.tsx

@@ -189,7 +189,7 @@ export default function AssistantChatPage() {
                   onChange={e => setInput(e.target.value)}
                   onKeyDown={handleKeyDown}
                   placeholder="Ask about IT, networking, troubleshooting..."
-                  rows={1}
+                  rows={3}
                   className="flex-1 resize-none rounded-xl border bg-card text-foreground text-sm placeholder:text-muted-foreground px-4 py-3 focus:outline-none focus:border-[rgba(6,182,212,0.3)]"
                   style={{ borderColor: 'var(--glass-border)' }}
                   disabled={loading}