Adapt economics dashboard to sole-member zero-cost reality

Update membership, revenue, and cost registries to one active member with
no running costs. Refresh dashboard report and tests for €8.99 revenue and
100% gross margin.

projects/coulomb-pricing/data/costs.json

@@ -1,64 +1,9 @@
 {
   "version": 1,
   "period": "2026-06",
-  "entries": [
-    {
-      "id": "bubble-subscription",
-      "name": "Bubble.io platform",
-      "category": "fixed",
-      "amount": "35.00",
-      "currency": "USD",
-      "cadence": "monthly",
-      "allocation": "flat"
-    },
-    {
-      "id": "domains",
-      "name": "Domains",
-      "category": "fixed",
-      "amount": "15.00",
-      "currency": "EUR",
-      "cadence": "monthly",
-      "allocation": "flat"
-    },
-    {
-      "id": "operational-overhead",
-      "name": "Operational overhead",
-      "category": "fixed",
-      "amount": "25.00",
-      "currency": "EUR",
-      "cadence": "monthly",
-      "allocation": "flat"
-    },
-    {
-      "id": "stripe-percentage",
-      "name": "Stripe percentage fee",
-      "category": "variable",
-      "amount": "0.015",
-      "currency": "ratio",
-      "cadence": "per_transaction",
-      "allocation": "percent_of_gross_revenue"
-    },
-    {
-      "id": "stripe-fixed",
-      "name": "Stripe fixed fee",
-      "category": "variable",
-      "amount": "0.25",
-      "currency": "EUR",
-      "cadence": "per_transaction",
-      "allocation": "per_active_member"
-    },
-    {
-      "id": "openrouter-ai",
-      "name": "OpenRouter AI consumption",
-      "category": "variable",
-      "amount": "0.00",
-      "currency": "EUR",
-      "cadence": "monthly",
-      "allocation": "flat",
-      "note": "Populated in Sprint 4 after usage import"
-    }
-  ],
+  "entries": [],
   "fx_rates": {
     "USD/EUR": "0.92"
-  }
+  },
+  "note": "No running costs at present. Future fixed/variable lines (Bubble, Stripe, OpenRouter) added as they become payable."
 }