feat: add locale formatting config and update notebook outputs

Add configurable locale/display formatting environment variables
(`PALLADIUM_CURRENCY_SYMBOL`, `PALLADIUM_THOUSANDS_SEP`,
`PALLADIUM_DECIMAL_SEP`) to support regional number formatting in the
Streamlit app. Update `.env.example` with documentation for these new
variables.

Also refresh `00_setup.ipynb` with current execution outputs reflecting
a live Athena connection with report templates, a selected client
(Global Guardian Insurance, ID=2), and resolved NameError in assumption
override cells.

app/views/costs.py

@@ -5,12 +5,17 @@ from __future__ import annotations
 import streamlit as st
 
 from app.components.tables import df_to_values, value_editor
-from app.pages._helpers import report_meta, safe
+from app.utils import icon
+
+from app.views._helpers import report_meta, safe
 from core.tei_client import TEIClient
 
 
 def render(client: TEIClient, tool: dict) -> None:
-    st.header("💸 Costs")
+    st.markdown(
+        f"<h2>{icon('receipt')} Costs</h2>",
+        unsafe_allow_html=True,
+    )
     public_id = tool["id"]
     report = report_meta(client, tool)
     analysis_years = int(report.get("analysis_period_years") or 3)
@@ -32,7 +37,8 @@ def render(client: TEIClient, tool: dict) -> None:
 
     col1, col2 = st.columns([1, 4])
     with col1:
-        if st.button("💾 Save costs", use_container_width=True):
+        if st.button("Save costs", width="stretch"):
+
             payload = df_to_values(edited, "costs", analysis_years)
             result = safe(client.update_values, public_id, payload)
             if result is not None: