refactor: restructure repo into core/app modules with per-study folders

Reorganize Palladium codebase into a modular architecture with `core/`
shared logic and `app/` Streamlit UI, separating per-study assets into
`studies/YYYYMM_<Vendor>/` folders containing notebooks, seed data, and
configuration. Update README to reflect new structure, add `.gitignore`
entries for `.env` and study exports, and refresh component documentation.

app/components/charts.py

@@ -0,0 +1,32 @@
+"""Streamlit-friendly chart wrappers (delegate to core.notebook_helpers.charts)."""
+
+from __future__ import annotations
+
+import streamlit as st
+
+from core.notebook_helpers import charts as core_charts
+
+
+def cashflow(yearly_breakdown, *, initial_cost: float = 0.0) -> None:
+    fig = core_charts.cashflow_chart(yearly_breakdown, initial_cost=initial_cost)
+    st.plotly_chart(fig, use_container_width=True)
+
+
+def benefits_bar(items) -> None:
+    fig = core_charts.benefits_bar(items)
+    st.plotly_chart(fig, use_container_width=True)
+
+
+def cost_pie(items) -> None:
+    fig = core_charts.cost_breakdown_pie(items)
+    st.plotly_chart(fig, use_container_width=True)
+
+
+def scenario_bars(scenarios) -> None:
+    fig = core_charts.scenario_comparison(scenarios)
+    st.plotly_chart(fig, use_container_width=True)
+
+
+def waterfall(values) -> None:
+    fig = core_charts.waterfall(values)
+    st.plotly_chart(fig, use_container_width=True)