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.
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.
