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.

studies/202602_AmazonConnect/config.py

@@ -0,0 +1,39 @@
+"""
+Study configuration for the Amazon Connect TEI (February 2026).
+
+Set ``TOOL_PUBLIC_ID`` to the public_id of the live TEI tool instance in
+Athena once it has been created. ``REPORT_PUBLIC_ID`` is the template
+this tool was created from (Athena admin sets up Report templates).
+
+Until both are filled in, the notebooks fall back to local-only mode:
+they compute summaries from ``seed_data.py`` using ``core.calculations``
+and skip the network round-trip.
+"""
+
+from __future__ import annotations
+
+import os
+
+#: Human-friendly study identifier — used in export metadata + filenames.
+STUDY_SLUG = "202602_AmazonConnect"
+
+#: TEI Report template public_id (12-char short UUID). Provisioned in
+#: Athena admin → TEI → Reports.
+REPORT_PUBLIC_ID: str = os.getenv("PALLADIUM_REPORT_PUBLIC_ID", "")
+
+#: TEI Tool instance public_id. Created via the API
+#: (``client.create_tool``) or the Streamlit app sidebar.
+TOOL_PUBLIC_ID: str = os.getenv("PALLADIUM_TOOL_PUBLIC_ID", "")
+
+#: Default discount rate used for local validation of the study numbers.
+DISCOUNT_RATE = 0.10
+
+#: Analysis horizon (years).
+ANALYSIS_YEARS = 3
+
+#: Optional Athena Proposal ID this tool is linked to (when known).
+PROPOSAL_ID: int | None = (
+    int(os.environ["PALLADIUM_PROPOSAL_ID"])
+    if os.getenv("PALLADIUM_PROPOSAL_ID")
+    else None
+)