feat: cola de jobs asincrona basada en SQLite (issue 0013)

Implementa el subsistema completo de background jobs para apps Go en el
dominio infra. 9 funciones + 3 tipos + 17 tests, todos pasando.

- Tipos: Job (product), JobQueue (product), JobStatus (sum) con
  JobHandler, EnqueueOption y WorkerOption usando functional options pattern
- job_queue_create: CREATE TABLE + indices + WAL mode
- job_enqueue: INSERT con UUID (github.com/google/uuid), WithPriority/WithScheduledAt/WithMaxAttempts
- job_dequeue: SELECT+UPDATE atomico en transaccion exclusiva, filtro por jobTypes
- job_complete / job_fail: transiciones de estado; fail → dead cuando attempts >= max_attempts
- job_status_summary: pura, formatea conteo de jobs por estado
- job_worker: poll loop bloqueante, context-cancelable, graceful shutdown
- job_worker_pool: N workers con golang.org/x/sync/errgroup
- job_cleanup: DELETE jobs terminales mas viejos que olderThan

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

types/infra/job.md

@@ -0,0 +1,31 @@
+---
+name: job
+lang: go
+domain: infra
+version: "1.0.0"
+algebraic: product
+definition: |
+  type Job struct {
+      ID          string
+      Type        string
+      Payload     string
+      Status      JobStatus
+      Priority    int
+      Attempts    int
+      MaxAttempts int
+      ScheduledAt time.Time
+      StartedAt   *time.Time
+      CompletedAt *time.Time
+      Result      *string
+      Error       *string
+      CreatedAt   time.Time
+  }
+description: "Unidad de trabajo asincrono almacenada en SQLite. Payload es un JSON string. Status evoluciona de pending a running y luego a completed, failed o dead."
+tags: [job, queue, async, background, sqlite, infra]
+uses_types: [job_status_go_infra]
+file_path: "functions/infra/job_queue_types.go"
+---
+
+## Notas
+
+Tipo producto. Los campos `StartedAt`, `CompletedAt`, `Result` y `Error` son punteros — son nil hasta que el job alcanza el estado correspondiente. `Payload` es siempre un JSON string (minimo "{}").

types/infra/job_queue.md

@@ -0,0 +1,20 @@
+---
+name: job_queue
+lang: go
+domain: infra
+version: "1.0.0"
+algebraic: product
+definition: |
+  type JobQueue struct {
+      DB        *sql.DB
+      TableName string
+  }
+description: "Handle para una cola de jobs SQLite. Wrappea un *sql.DB y el nombre de la tabla de jobs. Se crea con JobQueueCreate."
+tags: [job, queue, sqlite, infra, async]
+uses_types: []
+file_path: "functions/infra/job_queue_types.go"
+---
+
+## Notas
+
+Tipo producto minimo — todas las funciones del subsistema de jobs lo reciben como primer argumento. TableName permite tener multiples colas en la misma DB. Se crea con `JobQueueCreate`.

types/infra/job_status.md

@@ -0,0 +1,25 @@
+---
+name: job_status
+lang: go
+domain: infra
+version: "1.0.0"
+algebraic: sum
+definition: |
+  type JobStatus string
+
+  const (
+      JobStatusPending   JobStatus = "pending"
+      JobStatusRunning   JobStatus = "running"
+      JobStatusCompleted JobStatus = "completed"
+      JobStatusFailed    JobStatus = "failed"
+      JobStatusDead      JobStatus = "dead"
+  )
+description: "Estado del ciclo de vida de un job. Tipo suma con cinco variantes: pending, running, completed, failed, dead."
+tags: [job, status, queue, async, infra]
+uses_types: []
+file_path: "functions/infra/job_queue_types.go"
+---
+
+## Notas
+
+Tipo suma. Ciclo de vida normal: pending → running → completed. En error: pending → running → failed (reintentos posibles) → dead (sin mas intentos). Un job con `attempts >= max_attempts` pasa directamente a dead.