feat(F-003): HTTP foundation with request context and error envelope

- request_id generated or sanitized-propagated on every request (x-request-id)
- structured JSON logging (pino), one correlated line per request, injectable logger
- error envelope v2 { error: { statusCode, code, message, details? }, requestId }
- 5xx messages always generic; stack traces stay in server logs only
- explicit parseJson (zod) input validation hook at the API layer
- README HTTP contract section; deps justified in spec/tech.md
- all gates approved; verify.sh green

project/src/infrastructure/logging/logger.ts

@@ -0,0 +1,25 @@
+/**
+ * Structured JSON logging. pino is the boring, fast, Fastify-ecosystem choice.
+ * No pretty printers, no transports: JSON lines to a writable destination.
+ */
+import pino, { type DestinationStream, type Logger } from 'pino';
+
+const SERVICE_NAME = 'mercadodevida-backend';
+
+export interface LoggerOptions {
+  /** Log level; defaults to LOG_LEVEL env var or 'info'. */
+  level?: string;
+  /** Explicit destination stream (tests use an in-memory stream). */
+  destination?: DestinationStream;
+}
+
+export function createLogger(options: LoggerOptions = {}): Logger {
+  const level = options.level ?? process.env.LOG_LEVEL ?? 'info';
+  const settings = { level, base: { service: SERVICE_NAME } };
+  if (options.destination) {
+    return pino(settings, options.destination);
+  }
+  return pino(settings);
+}
+
+export type { Logger };