Refactor economics to expense-record ledger with correct Bubble cost

Replace pre-aggregated costs.json with expense_records.json (48 line-item
records) and payment_records.json. All monthly and cumulative totals are
computed deterministically in observatory/ledger.py. Correct Bubble.io to
$32/mo (since Feb 2025) — infrastructure €69.44/mo not €72.20.

projects/coulomb-pricing/observatory/dashboard.py

@@ -9,26 +9,27 @@ from .load import (
     default_data_dir,
     latest_period,
     load_budget,
+    load_expense_records,
     load_membership,
-    load_monthly_platform_costs,
+    load_monthly_ledger,
+    load_payment_records,
     load_pricing_models,
     load_product,
-    load_revenue,
 )
-from .models import EconomicsSnapshot, LiquiditySummary, MonthlyPlatformCost, PricingModel, Product, RevenueEntry
+from .models import EconomicsSnapshot, LiquiditySummary, MonthlyPlatformCost, PaymentRecord, PricingModel, Product
 
 
 def _history_rows(
     monthly_costs: list[MonthlyPlatformCost],
-    revenue_entries: list[RevenueEntry],
+    payments: list[PaymentRecord],
     through_period: str,
 ) -> str:
-    revenue_by_period = {entry.period: entry for entry in revenue_entries}
+    payment_by_period = {record.period: record for record in payments}
     lines: list[str] = []
     for month in sorted(monthly_costs, key=lambda item: item.period):
         if month.period > through_period:
             continue
-        payment = revenue_by_period.get(month.period)
+        payment = payment_by_period.get(month.period)
         net_payment = payment.net_amount if payment else Decimal("0")
         period_net = net_payment - month.infrastructure_cost
         lines.append(
@@ -45,14 +46,15 @@ def render_dashboard(
     snapshot: EconomicsSnapshot,
     liquidity: LiquiditySummary,
     monthly_costs: list[MonthlyPlatformCost],
-    revenue_entries: list[RevenueEntry],
+    payments: list[PaymentRecord],
+    expense_count: int,
 ) -> str:
     active = next(m for m in models if m.id == product.active_pricing_model_id)
     registry_lines = "\n".join(
         f"| {model.id} | {model.name} | {model.model_type} | {model.status} |"
         for model in models
     )
-    history_lines = _history_rows(monthly_costs, revenue_entries, snapshot.period)
+    history_lines = _history_rows(monthly_costs, payments, snapshot.period)
     budget_state = (
         "over budget"
         if liquidity.remaining_budget < Decimal("0")
@@ -66,7 +68,9 @@ def render_dashboard(
 **Active pricing model:** {active.name} ({active.access_fee_amount} {active.currency}/{active.access_fee_cadence})
 
 > Platform costs accrue to the operator. Customer cost-pass-through billing is
-> **not active** in MVP — members pay subscription only.
+> **not active** in MVP — members pay subscription only. All totals are computed
+> programmatically from expense and payment record ledgers ({expense_count} expense
+> records).
 
 ## Key Metrics (current period)
 
@@ -114,9 +118,8 @@ _Revenue source: {snapshot.revenue_source}_
 
 - Product model (`data/product.json`)
 - Budget (`data/budget.json`)
-- Pricing model registry (`data/pricing-models.json`)
-- Platform costs (`data/costs.json`)
-- Member payments (`data/revenue.json`)
+- Expense records (`data/expense_records.json`) — source of truth for costs
+- Payment records (`data/payment_records.json`)
 - Membership (`data/membership.json`)
 - Requirements (`REQUIREMENTS.md`)
 """
@@ -128,13 +131,16 @@ def generate_dashboard(data_dir: Path | None = None, period: str | None = None)
     budget = load_budget(root)
     models = load_pricing_models(root)
     members = load_membership(root)
-    revenue = load_revenue(root)
-    monthly_costs = load_monthly_platform_costs(root)
+    payments = load_payment_records(root)
+    expenses = load_expense_records(root)
+    monthly_costs = load_monthly_ledger(root)
     target_period = period or latest_period(monthly_costs)
 
-    snapshot = build_snapshot(target_period, product, models, members, revenue, monthly_costs)
-    liquidity = build_liquidity_summary(budget, revenue, monthly_costs, target_period)
-    return render_dashboard(product, models, snapshot, liquidity, monthly_costs, revenue)
+    snapshot = build_snapshot(target_period, product, models, members, payments, monthly_costs)
+    liquidity = build_liquidity_summary(budget, payments, monthly_costs, target_period)
+    return render_dashboard(
+        product, models, snapshot, liquidity, monthly_costs, payments, len(expenses)
+    )
 
 
 def main(argv: list[str] | None = None) -> int: