feat(enakgame): game sessions, rewards, vouchers, budgets and events

EnakGame phases 1-8 of docs/tasks-enakgame.md (EG-101 to EG-803), built on the
existing EnakPoint/EnakCoin wallet (docs/rfc-enakgame.md).

Foundation (phase 1)
- Migrations 000103-000106: games extended with organization, slug, status,
  entry cost and result rules, old games archived (not deleted); budgets,
  versioned reward configs, sessions and session rewards; the ledger types
  GAME_SPEND_REFUND, GAME_REWARD and REWARD_REDEEM_REFUND; audit_logs.
- AuditLogger writes in the caller's transaction only.
- enakgame.limit.user_daily and global_daily organization settings.

Games and sessions (phases 2-4)
- Admin /marketing/enakgame: games, reward config versions (immutable but for
  status, one ACTIVE per game), budgets with non-overlapping global periods and
  a daily job opening the next month.
- Customer /customer/enakgame: start (Idempotency-Key, entry cost and config
  frozen on the session), complete (result validation, reward engine, max_reward
  cap, daily limits via game_reward_counters, one GAME_REWARD per budget),
  automatic refunds for system errors and deactivated games, and a session job.
- Reward engine: FIXED, SCORE_BASED, OUTCOME_BASED, PROBABILITY (crypto/rand),
  rounded down.

Vouchers and budgets (phases 5-6)
- Migration 000108 and 000107: vouchers, codes, redemptions, cost attribution;
  Economy Guard counters.
- STATIC and CODE_POOL redemption in one transaction with the REDEEM PIN action;
  realized cost traced through the lots to the budget that paid the reward.
- Budget metrics: realized cost, forecast, exposure and status. Migrations
  000109-000110 add the wallet_lots indexes they need, built CONCURRENTLY.

Events (phase 7)
- Migration 000111: game events, each with its own EVENT budget. Event extras
  stack per PRD §16 defaults, with event and per-customer limits.

External vouchers (phase 8)
- VoucherProvider contract, two-step PENDING redemption and a recovery job,
  tested with a fake provider. No provider adapter is registered yet, so
  EXTERNAL vouchers stay out of the catalog.

Not yet decided before release: reward rounding, event stacking, budget
exhaustion policy and thresholds (RFC §19.2). Migrations 000103-000111 have
not been run on any shared database.

Also fixes a leftover PAYMENT filter in a wallet test and a data race in a
test PIN fake.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/processor/voucher_provider.go

@@ -0,0 +1,76 @@
+package processor
+
+import (
+	"context"
+	"errors"
+
+	"github.com/google/uuid"
+)
+
+var (
+	// ErrVoucherProviderRejected is what an adapter wraps when the provider definitely
+	// will not issue the voucher: out of stock, the product retired, the request
+	// refused. The redemption fails and the EnakPoint go back.
+	ErrVoucherProviderRejected = errors.New("voucher provider refused")
+	// ErrVoucherProviderNotFound is what an adapter's Lookup wraps when the provider
+	// has no record of the redemption: the issue request never reached it.
+	ErrVoucherProviderNotFound = errors.New("voucher provider has no such redemption")
+)
+
+// VoucherIssueRequest is one redemption of an EXTERNAL voucher sent to its provider.
+type VoucherIssueRequest struct {
+	// The provider's idempotency key: asking twice for the same redemption must give
+	// the same voucher, never a second one (docs/rfc-enakgame.md §7.5).
+	RedemptionID uuid.UUID
+	// The provider's own reference of the product, from vouchers.provider_ref.
+	ProviderRef *string
+	VoucherID   uuid.UUID
+	FaceValue   int64
+	CustomerID  uuid.UUID
+}
+
+// VoucherIssue is what a provider handed out.
+type VoucherIssue struct {
+	Code string
+	// The provider's reference of this issue, for support and reconciliation.
+	Ref string
+}
+
+// VoucherProvider issues EXTERNAL vouchers (EG-801). Adapters classify every outcome
+// through the error they return:
+//
+//   - nil: issued.
+//   - wrapping ErrVoucherProviderRejected: definitely not issued, and never will be.
+//   - wrapping ErrVoucherProviderNotFound (Lookup only): the provider never got it.
+//   - anything else, a timeout above all: unknown. The redemption stays PENDING and
+//     the recovery job asks again.
+type VoucherProvider interface {
+	Issue(ctx context.Context, req VoucherIssueRequest) (*VoucherIssue, error)
+	Lookup(ctx context.Context, req VoucherIssueRequest) (*VoucherIssue, error)
+}
+
+// VoucherProviders are the adapters by the name vouchers.provider holds.
+type VoucherProviders map[string]VoucherProvider
+
+// voucherIssueOutcome is how one call to a provider ended.
+type voucherIssueOutcome int
+
+const (
+	voucherIssued voucherIssueOutcome = iota
+	voucherRejected
+	voucherUnknown
+	voucherNotFound
+)
+
+func classifyVoucherIssue(issue *VoucherIssue, err error) voucherIssueOutcome {
+	switch {
+	case err == nil && issue != nil && issue.Code != "":
+		return voucherIssued
+	case errors.Is(err, ErrVoucherProviderRejected):
+		return voucherRejected
+	case errors.Is(err, ErrVoucherProviderNotFound):
+		return voucherNotFound
+	}
+	// An error of any other kind, or a success without a code, settles nothing.
+	return voucherUnknown
+}