Fix cumulative platform cost Stripe double-counting

Split infrastructure vs payment-processing costs. Liquidity burn now
uses infrastructure cash out only (€1,155.20 cumulative) because Stripe
fees are already deducted from net member payments. Total platform cost
(€1,158.24) remains visible for gross-margin economics.

projects/coulomb-pricing/observatory/load.py

@@ -4,6 +4,8 @@ import json
 from decimal import Decimal
 from pathlib import Path
 
+_ZERO = Decimal("0")
+
 from .models import (
     Budget,
     CostEntry,
@@ -89,15 +91,25 @@ def load_cost_rate_card(data_dir: Path | None = None) -> tuple[list[CostEntry],
 
 def load_monthly_platform_costs(data_dir: Path | None = None) -> list[MonthlyPlatformCost]:
     raw = _read_json((data_dir or default_data_dir()) / "costs.json")
-    return [
-        MonthlyPlatformCost(
-            period=item["period"],
-            platform_cost=_money(item["platform_cost"]),
-            active_members=item["active_members"],
-            gross_revenue=_money(item["gross_revenue"]),
+    rows: list[MonthlyPlatformCost] = []
+    for item in raw.get("monthly_history", []):
+        if "infrastructure_cost" in item:
+            infrastructure = _money(item["infrastructure_cost"])
+            processing = _money(item.get("payment_processing_cost", "0"))
+        else:
+            # Legacy single platform_cost field treated as infrastructure only.
+            infrastructure = _money(item["platform_cost"])
+            processing = _ZERO
+        rows.append(
+            MonthlyPlatformCost(
+                period=item["period"],
+                infrastructure_cost=infrastructure,
+                payment_processing_cost=processing,
+                active_members=item["active_members"],
+                gross_revenue=_money(item["gross_revenue"]),
+            )
         )
-        for item in raw.get("monthly_history", [])
-    ]
+    return rows
 
 
 def load_revenue(data_dir: Path | None = None) -> list[RevenueEntry]: