feat(ads): rewarded video (VK) — client-attested credit + daily/hourly caps

The first ads slice: a voluntary rewarded video credits chips. VK Mini App ads
(VKWebAppShowNativeAds) expose only a client-side watch result — no
server-to-server verify — so the credit is client-attested, guarded by a server
daily + hourly cap (config reward_daily_cap / reward_hourly_cap, default 50 / 10).
The caps are both anti-abuse (bounding a forger who skips the ad and calls the
endpoint directly) and an economic conversion lever (limiting free chips so a
player who wants more buys). D29 amended to VK's reality.

Backend: CreditReward (VK-only, order-less, idempotent on a client nonce, floored
by the caps; payout from config rewarded_payout_chips, default 0 = off) + the
wallet.reward edge op returning the updated wallet (reward_chips gates the
"watch for chips" CTA). Additive migration (two config columns).

Client: the ads-network abstraction (lib/ads.ts, VK impl) + the VK bridge
(vkRewardedReady / vkShowRewarded) + the Wallet CTA + i18n. A contour test stub
(VITE_ADS_STUB -> a toast instead of a real ad; prod always real) and a temporary
diagnostic that logs the raw VK data, so we confirm on the contour exactly what
VK returns (harden to signature-verify if it carries one).

Tests: backend integration (credit, nonce idempotency, hourly cap, disabled,
non-VK refusal) + codec unit (reward wire). Docs: PAYMENTS(+ru) §10, D29 amend,
PLAN E6. Bundle: shared budget 30->31 (reward i18n strings).

backend/internal/postgres/jet/payments/table/config.go

@@ -23,6 +23,8 @@ type configTable struct {
 	CooldownVsAiSeconds   postgres.ColumnInteger
 	CooldownHintSeconds   postgres.ColumnInteger
 	OrderTTLSeconds       postgres.ColumnInteger
+	RewardDailyCap        postgres.ColumnInteger
+	RewardHourlyCap       postgres.ColumnInteger
 
 	AllColumns     postgres.ColumnList
 	MutableColumns postgres.ColumnList
@@ -70,9 +72,11 @@ func newConfigTableImpl(schemaName, tableName, alias string) configTable {
 		CooldownVsAiSecondsColumn   = postgres.IntegerColumn("cooldown_vs_ai_seconds")
 		CooldownHintSecondsColumn   = postgres.IntegerColumn("cooldown_hint_seconds")
 		OrderTTLSecondsColumn       = postgres.IntegerColumn("order_ttl_seconds")
-		allColumns                  = postgres.ColumnList{OnlyRowColumn, RewardedPayoutChipsColumn, CooldownGlobalSecondsColumn, CooldownVsAiSecondsColumn, CooldownHintSecondsColumn, OrderTTLSecondsColumn}
-		mutableColumns              = postgres.ColumnList{RewardedPayoutChipsColumn, CooldownGlobalSecondsColumn, CooldownVsAiSecondsColumn, CooldownHintSecondsColumn, OrderTTLSecondsColumn}
-		defaultColumns              = postgres.ColumnList{OnlyRowColumn, RewardedPayoutChipsColumn, CooldownGlobalSecondsColumn, CooldownVsAiSecondsColumn, CooldownHintSecondsColumn, OrderTTLSecondsColumn}
+		RewardDailyCapColumn        = postgres.IntegerColumn("reward_daily_cap")
+		RewardHourlyCapColumn       = postgres.IntegerColumn("reward_hourly_cap")
+		allColumns                  = postgres.ColumnList{OnlyRowColumn, RewardedPayoutChipsColumn, CooldownGlobalSecondsColumn, CooldownVsAiSecondsColumn, CooldownHintSecondsColumn, OrderTTLSecondsColumn, RewardDailyCapColumn, RewardHourlyCapColumn}
+		mutableColumns              = postgres.ColumnList{RewardedPayoutChipsColumn, CooldownGlobalSecondsColumn, CooldownVsAiSecondsColumn, CooldownHintSecondsColumn, OrderTTLSecondsColumn, RewardDailyCapColumn, RewardHourlyCapColumn}
+		defaultColumns              = postgres.ColumnList{OnlyRowColumn, RewardedPayoutChipsColumn, CooldownGlobalSecondsColumn, CooldownVsAiSecondsColumn, CooldownHintSecondsColumn, OrderTTLSecondsColumn, RewardDailyCapColumn, RewardHourlyCapColumn}
 	)
 
 	return configTable{
@@ -85,6 +89,8 @@ func newConfigTableImpl(schemaName, tableName, alias string) configTable {
 		CooldownVsAiSeconds:   CooldownVsAiSecondsColumn,
 		CooldownHintSeconds:   CooldownHintSecondsColumn,
 		OrderTTLSeconds:       OrderTTLSecondsColumn,
+		RewardDailyCap:        RewardDailyCapColumn,
+		RewardHourlyCap:       RewardHourlyCapColumn,
 
 		AllColumns:     allColumns,
 		MutableColumns: mutableColumns,