Refine radio button border styling: Reduce border thickness

Adjusted the radio button CSS border from 2px to 0.5px, creating a subtler border definition while maintaining the existing styling approach.

app.py

@@ -59,7 +59,7 @@ st.markdown("""
         gap: 1px;
         font-weight: bold;
         transition: all 0.3s ease;
-        border: 2px solid black;
+        border: .5px solid black;
     }
             
     .stRadio [tabindex="0"] {