refactor: rename pages directory to views

Renames the `app/pages` module to `app/views` to better reflect the
purpose of the directory, aligning with conventional MVC naming
conventions where view-related logic is housed under `views`.

app/views/summary.py

@@ -0,0 +1,118 @@
+"""Financial summary dashboard tab."""
+
+from __future__ import annotations
+
+import streamlit as st
+
+from app.components import charts
+from app.pages._helpers import report_meta, safe
+from core.export import build_report_data
+from core.tei_client import AthenaAPIError, TEIClient
+
+
+def render(client: TEIClient, tool: dict) -> None:
+    st.header("📊 Financial Summary")
+    public_id = tool["id"]
+    report = report_meta(client, tool)
+
+    try:
+        summary = client.get_summary(public_id)
+    except AthenaAPIError as e:
+        if e.status_code == 404:
+            st.info(
+                "No summary yet — click **Recalculate** in the sidebar after "
+                "filling in benefits and costs."
+            )
+            return
+        st.error(f"Athena API error: {e.detail}")
+        return
+
+    npv = float(summary.get("net_present_value") or summary.get("npv") or 0)
+    roi = float(
+        summary.get("roi_percentage")
+        or summary.get("roi")
+        or summary.get("roi_pct")
+        or 0
+    )
+    payback = summary.get("payback_period_months", summary.get("payback_months"))
+    bpv = float(summary.get("total_benefits_pv") or 0)
+    cpv = float(summary.get("total_costs_pv") or 0)
+
+    cols = st.columns(5)
+    cols[0].metric("NPV", f"${npv/1_000_000:,.1f}M")
+    cols[1].metric("ROI", f"{roi:,.0f}%")
+    cols[2].metric(
+        "Payback",
+        f"{float(payback):.1f} months" if payback is not None else "N/A",
+    )
+    cols[3].metric("Benefits PV", f"${bpv/1_000_000:,.1f}M")
+    cols[4].metric("Costs PV", f"${cpv/1_000_000:,.1f}M")
+
+    st.divider()
+
+    # Build the yearly breakdown from the documented per-year summary keys
+    # (benefits_year_N / costs_year_N) when no pre-built breakdown exists.
+    yb = summary.get("yearly_breakdown") or []
+    if not yb:
+        n = 1
+        while f"benefits_year_{n}" in summary or f"costs_year_{n}" in summary:
+            b = float(summary.get(f"benefits_year_{n}") or 0)
+            c = float(summary.get(f"costs_year_{n}") or 0)
+            yb.append({"year": n, "benefits": b, "costs": c, "net": b - c})
+            n += 1
+    initial = float(summary.get("initial_costs") or 0)
+    if yb:
+        charts.cashflow(yb, initial_cost=initial)
+        with st.expander("Cash flow table"):
+            st.dataframe(yb, use_container_width=True, hide_index=True)
+    else:
+        st.caption("No yearly breakdown in this summary.")
+
+    # Scenario comparison — computed locally from current values
+    with st.expander("Scenario analysis (conservative / moderate / aggressive)"):
+        envelope = safe(
+            build_report_data,
+            client,
+            public_id,
+            include_scenarios=True,
+            study_slug=report.get("name", ""),
+        )
+        if envelope and envelope.get("scenarios"):
+            charts.scenario_bars(envelope["scenarios"])
+            rows = [
+                {
+                    "Scenario": k,
+                    "Benefits PV": float(v.get("total_benefits_pv") or 0),
+                    "Costs PV": float(v.get("total_costs_pv") or 0),
+                    "NPV": float(v.get("npv") or 0),
+                    "ROI %": float(v.get("roi_pct") or 0),
+                    "Payback (months)": (
+                        round(float(v.get("payback_months") or 0), 1)
+                        if v.get("payback_months") is not None
+                        else None
+                    ),
+                }
+                for k, v in envelope["scenarios"].items()
+            ]
+            st.dataframe(rows, use_container_width=True, hide_index=True)
+
+    # Export button
+    st.divider()
+    if st.button("📦 Build export envelope (JSON)"):
+        envelope = safe(
+            build_report_data,
+            client,
+            public_id,
+            include_scenarios=True,
+            study_slug=report.get("name", ""),
+        )
+        if envelope:
+            import json
+
+            data = json.dumps(envelope, indent=2, default=str)
+            st.download_button(
+                "Download export.json",
+                data=data,
+                file_name=f"{public_id}_export.json",
+                mime="application/json",
+            )