unsafe_allow_html=True with hardcoded HTML in sidebar

[AshayK003]

Problem

sidebar.py:280 uses unsafe_allow_html=True to render a hardcoded donation link. Sets a bad precedent for future XSS.

Solution

Replace with Streamlit's native st.markdown("[text](url)") link syntax.

Acceptance Criteria

• Donation link renders correctly without unsafe_allow_html

Difficulty: Easy