Task #6: Cost-based work fee pricing with BTC oracle

## New files
- btc-oracle.ts: CoinGecko BTC/USD fetch (60s cache), usdToSats() helper (ceil, min 1 sat),
  5s abort timeout, fallback to BTC_PRICE_USD_FALLBACK env var (default $100k)
- lib/db/migrations/0002_cost_based_pricing.sql: SQL migration artifact adding 6 new columns
  to jobs table (estimated_cost_usd, margin_pct, btc_price_usd, actual_input_tokens,
  actual_output_tokens, actual_cost_usd); idempotent via ADD COLUMN IF NOT EXISTS

## Modified files
- pricing.ts: Full rewrite — per-model token rates (Haiku/Sonnet, env-var overridable),
  DO infra amortisation per request, originator margin %, estimateInputTokens/Output by tier,
  calculateActualCostUsd() for post-work ledger, async calculateWorkFeeSats() → WorkFeeBreakdown
- agent.ts: WorkResult now includes inputTokens + outputTokens from Anthropic usage;
  workModel/evalModel exposed as readonly public; EVAL_MODEL/WORK_MODEL env var support
- lib/db/src/schema/jobs.ts: 6 new real/integer columns; schema pushed to DB
- jobs.ts route: Work invoice creation calls pricingService.calculateWorkFeeSats() async;
  stores estimatedCostUsd/marginPct/btcPriceUsd; post-work stores actualInputTokens/
  actualOutputTokens/actualCostUsd; GET response includes pricingBreakdown and costLedger
  with totalTokens (input + output computed field)
- openapi.yaml: PricingBreakdown + CostLedger schemas (with totalTokens) added
- lib/api-zod/src/generated/api.ts: Regenerated with new schemas
- lib/api-client-react/src/generated/api.schemas.ts: Regenerated (PricingBreakdown, CostLedger)
- replit.md: 17 new env vars documented in cost-based pricing section

lib/api-client-react/src/generated/api.schemas.ts

@@ -40,13 +40,42 @@ export const JobState = {
   failed: "failed",
 } as const;
 
+/**
+ * Cost breakdown shown with the work invoice (estimations at invoice-creation time)
+ */
+export interface PricingBreakdown {
+  /** Total estimated cost in USD (token cost + DO infra + margin) */
+  estimatedCostUsd?: number;
+  /** Originator margin percentage applied */
+  marginPct?: number;
+  /** BTC/USD spot price used to convert the invoice to sats */
+  btcPriceUsd?: number;
+}
+
+/**
+ * Actual cost record stored after the job completes
+ */
+export interface CostLedger {
+  actualInputTokens?: number;
+  actualOutputTokens?: number;
+  /** Sum of actualInputTokens + actualOutputTokens */
+  totalTokens?: number;
+  /** Raw Anthropic token cost (no infra, no margin) */
+  actualCostUsd?: number;
+  estimatedCostUsd?: number;
+  marginPct?: number;
+  btcPriceUsd?: number;
+}
+
 export interface JobStatusResponse {
   jobId: string;
   state: JobState;
   evalInvoice?: InvoiceInfo;
   workInvoice?: InvoiceInfo;
+  pricingBreakdown?: PricingBreakdown;
   reason?: string;
   result?: string;
+  costLedger?: CostLedger;
   errorMessage?: string;
 }