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_cost.go

@@ -0,0 +1,43 @@
+package processor
+
+import (
+	"math/big"
+
+	"apskel-pos-be/internal/repository"
+)
+
+// VoucherCostPart is the share of a redemption's face value one source of its
+// EnakPoint accounts for (docs/rfc-enakgame.md §7.6).
+type VoucherCostPart struct {
+	repository.RedemptionPointSource
+	Cost int64
+}
+
+// SplitVoucherCost divides faceValue over the sources in proportion to their
+// EnakPoint: floor(face_value × points / total points) each, with what rounding left
+// over going to the largest part (the first of equals), so the parts add up to
+// face_value exactly. Products are computed without overflow.
+func SplitVoucherCost(faceValue int64, sources []repository.RedemptionPointSource) []VoucherCostPart {
+	parts := make([]VoucherCostPart, 0, len(sources))
+	var totalPoints int64
+	for _, s := range sources {
+		totalPoints += s.Points
+	}
+	if totalPoints <= 0 {
+		return parts
+	}
+	face, total := big.NewInt(faceValue), big.NewInt(totalPoints)
+	var assigned int64
+	largest := 0
+	for i, s := range sources {
+		share := new(big.Int).Mul(face, big.NewInt(s.Points))
+		share.Quo(share, total)
+		parts = append(parts, VoucherCostPart{RedemptionPointSource: s, Cost: share.Int64()})
+		assigned += share.Int64()
+		if s.Points > sources[largest].Points {
+			largest = i
+		}
+	}
+	parts[largest].Cost += faceValue - assigned
+	return parts
+}