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/REQUIREMENTS.md

@@ -11,15 +11,20 @@ The Economic Observatory must make the resulting **liquidity burn** visible.
 
 ## Requirements
 
-### LQ-001 — Platform cost ledger
+### LQ-001 — Expense record ledger (source of truth)
 
-Record monthly platform costs from project start (March 2025), including fixed
-infrastructure and payment-provider variable fees when member revenue exists.
+Capture every operator expense as an individual record in
+`data/expense_records.json`. Fields: `period`, `vendor`, `amount`, `currency`,
+`cost_class`, `source`.
 
-### LQ-002 — Member payment ledger
+**Never store hand-calculated monthly or cumulative totals in data files.**
+All aggregations must be computed programmatically by `observatory/ledger.py`.
 
-Record member subscription payments from first payment month (November 2025),
-separate from platform cost accrual.
+### LQ-002 — Payment record ledger
+
+Capture member subscription payments in `data/payment_records.json` with gross,
+fees, and net amounts per period. Payment-processing totals are summed from
+`fees_amount` — not duplicated as expense records.
 
 ### LQ-003 — Budget tracking
 
@@ -36,18 +41,15 @@ liquidity each period:
 - `cumulative_net = sum(period_net)`
 - `remaining_budget = initial_budget + cumulative_net`
 
-**No double-counting:** payment-processing fees (Stripe) are deducted from net
-member payments. They are tracked separately for economics reporting but must
-**not** be subtracted again in the liquidity formula.
+**No double-counting:** payment-processing fees are deducted from net member
+payments. They are summed separately for economics reporting but must **not** be
+subtracted again in the liquidity formula.
 
 - `total_platform_cost = infrastructure_cost + payment_processing_cost` (for
   gross-margin economics vs gross revenue)
 - `cumulative_total_platform_cost` is informational; liquidity burn uses
   `cumulative_infrastructure_cost` only
 
-Negative remaining budget means the MVP has consumed more liquidity than the
-allocated budget.
-
 ### LQ-005 — No customer cost billing (MVP boundary)
 
 Do not allocate platform costs to customer invoices in MVP. Cost attribution
@@ -60,16 +62,22 @@ Economics Dashboard must show:
 
 - Current-period economics (revenue, platform cost, margin)
 - Cumulative liquidity summary (budget, burn, remaining)
-- Monthly history table from March 2025
+- Monthly history table computed from ledgers
+
+### LQ-007 — Deterministic calculation engine
+
+All economics and liquidity figures must be produced by the Python observatory
+package (`ledger.py`, `economics.py`). LLM or manual arithmetic must not be the
+source of aggregated totals.
 
 ## Data sources (current)
 
-| Registry | Path |
-|----------|------|
+| Ledger | Path |
+|--------|------|
 | Budget | `data/budget.json` |
-| Platform costs | `data/costs.json` (`rate_card` + `monthly_history`) |
-| Member payments | `data/revenue.json` |
+| Expense records | `data/expense_records.json` |
+| Payment records | `data/payment_records.json` |
 | Membership | `data/membership.json` |
 
-Future sprints replace manual history with Bubble, Stripe, and OpenRouter imports
-while preserving the same liquidity semantics.
+Future sprints replace manual records with Bubble, Stripe, and OpenRouter imports
+while preserving the same ledger schema and calculation rules.