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.

.env.example

@@ -10,3 +10,16 @@ ATHENA_API_KEY=your-api-key-here
 # PALLADIUM_TOOL_PUBLIC_ID=
 # PALLADIUM_PROPOSAL_ID=
 # PALLADIUM_ENGAGEMENT_ID=
+
+# ---------------------------------------------------------------------------
+# Locale / display formatting (Streamlit app)
+# ---------------------------------------------------------------------------
+# Currency symbol prefix (default: $)
+# PALLADIUM_CURRENCY_SYMBOL=$
+#
+# Thousands separator (default: , for Americas/UK; use . for continental Europe)
+# PALLADIUM_THOUSANDS_SEP=,
+#
+# Decimal separator (default: . for Americas/UK; use , for continental Europe)
+# PALLADIUM_DECIMAL_SEP=.
+