style: add footer to landing page markdown screen

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

Author: crackcode09

app.py

@@ -73,6 +73,15 @@
 
 > **Pp and Ppk** use the same formulas but with long-term (overall) variation instead of short-term — they reflect actual historical performance rather than potential capability.
 """)
+    st.divider()
+    st.markdown(
+        "<div style='text-align: center; color: #98B1BE; font-size: 0.85rem;'>"
+        "Built by <strong>Nidhin Dileepkumar</strong> · Open Source · "
+        "Questions or feedback? "
+        "<a href='https://github.com/crackcode09/spc-control-chart-tool' style='color: #0078E6;'>View on GitHub</a>"
+        "</div>",
+        unsafe_allow_html=True,
+    )
     st.stop()
 
 try: