feat: add interactive exploration of Shannon's capacity formula with Plotly graphs

- Implemented bandwidth sensitivity and power sensitivity plots.
- Created a contour map for bit rate multiplying factors.
- Added input parameters for C/N and bandwidth with validation.
- Displayed computed results and sensitivity analysis metrics.
- Integrated interactive graphs for user exploration.
- Included background information section for user guidance.

views/contributions.py

@@ -0,0 +1,130 @@
+"""
+Page 3: Community Contributions
+
+Read, write, search and delete user contributions stored in SQLite.
+"""
+
+import streamlit as st
+from core.database import write_contribution, search_contributions, delete_contribution
+
+
+def render():
+    """Render the Contributions page."""
+
+    st.markdown("# 💬 Community Contributions")
+    st.markdown(
+        "Share your observations about Shannon's theorem, satellite communications, "
+        "or suggest improvements. Contributions are stored locally and shared with all users."
+    )
+
+    tab_read, tab_write = st.tabs(["📖 Read Contributions", "✍️ Write Contribution"])
+
+    # ── Read Contributions ──
+    with tab_read:
+        st.markdown("### 🔍 Search Contributions")
+
+        db_choice = st.radio(
+            "Database",
+            ["Theory", "Real World"],
+            horizontal=True,
+            key="db_read",
+        )
+        db_name = "Shannon_Theory.db" if db_choice == "Theory" else "Shannon_Real.db"
+
+        col_f1, col_f2 = st.columns(2)
+        with col_f1:
+            name_filter = st.text_input("Filter by Name", key="filter_name")
+            title_filter = st.text_input("Filter by Title", key="filter_title")
+        with col_f2:
+            kw_filter = st.text_input("Filter by Keywords", key="filter_kw")
+            content_filter = st.text_input("Filter by Content", key="filter_content")
+
+        if st.button("🔍 Search", type="primary", key="btn_search"):
+            results = search_contributions(
+                db_name,
+                name_filter=name_filter,
+                title_filter=title_filter,
+                keywords_filter=kw_filter,
+                content_filter=content_filter,
+            )
+            st.session_state["contrib_results"] = results
+
+        results = st.session_state.get("contrib_results", [])
+
+        if results:
+            st.success(f"Found {len(results)} contribution(s).")
+            for i, contrib in enumerate(results):
+                with st.expander(
+                    f"#{contrib['num']} — {contrib['title']} by {contrib['name']} ({contrib['date']})",
+                    expanded=(i == 0),
+                ):
+                    st.markdown(contrib["text"])
+                    if contrib["keywords"]:
+                        st.caption(f"🏷️ Keywords: {contrib['keywords']}")
+
+                    # Delete functionality
+                    with st.popover("🗑️ Delete"):
+                        st.warning("This action cannot be undone.")
+                        del_password = st.text_input(
+                            "Enter contribution password",
+                            type="password",
+                            key=f"del_pw_{contrib['num']}",
+                        )
+                        if st.button("Confirm Delete", key=f"del_btn_{contrib['num']}"):
+                            if delete_contribution(db_name, contrib["num"], del_password):
+                                st.success(f"✅ Contribution #{contrib['num']} deleted.")
+                                # Refresh results
+                                st.session_state["contrib_results"] = search_contributions(
+                                    db_name,
+                                    name_filter=name_filter,
+                                    title_filter=title_filter,
+                                    keywords_filter=kw_filter,
+                                    content_filter=content_filter,
+                                )
+                                st.rerun()
+                            else:
+                                st.error("❌ Incorrect password or contribution not found.")
+        elif "contrib_results" in st.session_state:
+            st.info("No contributions found matching your filters.")
+
+    # ── Write Contribution ──
+    with tab_write:
+        st.markdown("### ✍️ New Contribution")
+
+        db_choice_w = st.radio(
+            "Database",
+            ["Theory", "Real World"],
+            horizontal=True,
+            key="db_write",
+        )
+        db_name_w = "Shannon_Theory.db" if db_choice_w == "Theory" else "Shannon_Real.db"
+
+        with st.form("contribution_form", clear_on_submit=True):
+            name = st.text_input("Your Name / Initials *", max_chars=100)
+            title = st.text_input("Title *", max_chars=200)
+            keywords = st.text_input("Keywords (comma-separated)", max_chars=200)
+            text = st.text_area("Your contribution *", height=200)
+            password = st.text_input(
+                "Password (optional — leave empty to allow anyone to delete)",
+                type="password",
+            )
+
+            submitted = st.form_submit_button("📤 Submit", type="primary")
+
+            if submitted:
+                if not name or not title or not text:
+                    st.error("❌ Please fill in all required fields (marked with *).")
+                else:
+                    new_id = write_contribution(db_name_w, name, title, keywords, text, password)
+                    st.success(f"✅ Thank you! Your contribution has been stored with ID #{new_id}.")
+                    st.balloons()
+
+        with st.expander("❓ Help"):
+            st.markdown(
+                "Write your contribution as a free text. Contributions should be:\n\n"
+                "- Candid observations about the technical subject\n"
+                "- References to relevant material (ideally as web links)\n"
+                "- Open discussion items about adjacent subjects\n"
+                "- Suggestions for improvement\n\n"
+                "You can retrieve and delete your contribution from the Read tab using your password."
+            )