feat(payments): chip wallet, store-compliance gate and benefit application

Stand up the internal chip/benefit mechanic behind the narrow payments interface:
context-aware balances and benefits, an atomic chip spend, admin grants as
zero-price value sales, the one-directional store-compliance gate (VK/TG same-
origin only, web draws direct→vk→tg, VK-iOS frozen, untrusted fail-closed), and
per-origin hint and no-ads application with term stacking. Reads are served from
an in-process, account-keyed write-through cache (mirroring the suspension gate),
so hot paths issue no query to the payments schema.

Flip the online-game hint wallet and the ad-banner suppression from the deprecated
accounts.hint_balance / paid_account columns to the payments benefit (a hint
balance no longer suppresses the banner — only a no-ads benefit does), and fold
chip segments and benefits by origin on account merge, inside the merge tx. Add
the GET/POST /api/v1/user/wallet edge chain (REST → Connect → FlatBuffers) plus
its codec unit test; no wallet UI yet.

Bring the frozen owner decisions log into the repo at
docs/PAYMENTS_DECISIONS_ru.md (it was untracked under .vscode) and reference it
from PLAN.md; record the read-cache design and the present-sources interface in
PLAN.md and docs/PAYMENTS.md (+ RU mirror).

pkg/fbs/scrabble.fbs

@@ -848,3 +848,27 @@ table NotificationEvent {
   invitation:Invitation;
   state:StateView;
 }
+
+// WalletSegment is one chip balance in the wallet view: the funding source
+// ("vk"/"telegram"/"direct"), the chip count, and whether it is spendable in the current
+// execution context (false for a frozen VK-iOS balance or an untrusted platform).
+table WalletSegment {
+  source:string;
+  chips:int;
+  spendable:bool;
+}
+
+// Wallet is the user-facing wallet: the context-visible chip segments and the context-applicable
+// benefits — the no-ads term end as unix milliseconds (0 = no active term) or the perpetual
+// forever flag, and the available hint count.
+table Wallet {
+  segments:[WalletSegment];
+  ads_forever:bool;
+  ads_paid_until_ms:long;
+  hints:int;
+}
+
+// WalletBuyRequest buys a chip-priced value with chips: the product to buy.
+table WalletBuyRequest {
+  product_id:string;
+}

pkg/fbs/scrabblefb/Wallet.go

@@ -0,0 +1,120 @@
+// Code generated by the FlatBuffers compiler. DO NOT EDIT.
+
+package scrabblefb
+
+import (
+	flatbuffers "github.com/google/flatbuffers/go"
+)
+
+type Wallet struct {
+	_tab flatbuffers.Table
+}
+
+func GetRootAsWallet(buf []byte, offset flatbuffers.UOffsetT) *Wallet {
+	n := flatbuffers.GetUOffsetT(buf[offset:])
+	x := &Wallet{}
+	x.Init(buf, n+offset)
+	return x
+}
+
+func FinishWalletBuffer(builder *flatbuffers.Builder, offset flatbuffers.UOffsetT) {
+	builder.Finish(offset)
+}
+
+func GetSizePrefixedRootAsWallet(buf []byte, offset flatbuffers.UOffsetT) *Wallet {
+	n := flatbuffers.GetUOffsetT(buf[offset+flatbuffers.SizeUint32:])
+	x := &Wallet{}
+	x.Init(buf, n+offset+flatbuffers.SizeUint32)
+	return x
+}
+
+func FinishSizePrefixedWalletBuffer(builder *flatbuffers.Builder, offset flatbuffers.UOffsetT) {
+	builder.FinishSizePrefixed(offset)
+}
+
+func (rcv *Wallet) Init(buf []byte, i flatbuffers.UOffsetT) {
+	rcv._tab.Bytes = buf
+	rcv._tab.Pos = i
+}
+
+func (rcv *Wallet) Table() flatbuffers.Table {
+	return rcv._tab
+}
+
+func (rcv *Wallet) Segments(obj *WalletSegment, j int) bool {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(4))
+	if o != 0 {
+		x := rcv._tab.Vector(o)
+		x += flatbuffers.UOffsetT(j) * 4
+		x = rcv._tab.Indirect(x)
+		obj.Init(rcv._tab.Bytes, x)
+		return true
+	}
+	return false
+}
+
+func (rcv *Wallet) SegmentsLength() int {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(4))
+	if o != 0 {
+		return rcv._tab.VectorLen(o)
+	}
+	return 0
+}
+
+func (rcv *Wallet) AdsForever() bool {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(6))
+	if o != 0 {
+		return rcv._tab.GetBool(o + rcv._tab.Pos)
+	}
+	return false
+}
+
+func (rcv *Wallet) MutateAdsForever(n bool) bool {
+	return rcv._tab.MutateBoolSlot(6, n)
+}
+
+func (rcv *Wallet) AdsPaidUntilMs() int64 {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(8))
+	if o != 0 {
+		return rcv._tab.GetInt64(o + rcv._tab.Pos)
+	}
+	return 0
+}
+
+func (rcv *Wallet) MutateAdsPaidUntilMs(n int64) bool {
+	return rcv._tab.MutateInt64Slot(8, n)
+}
+
+func (rcv *Wallet) Hints() int32 {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(10))
+	if o != 0 {
+		return rcv._tab.GetInt32(o + rcv._tab.Pos)
+	}
+	return 0
+}
+
+func (rcv *Wallet) MutateHints(n int32) bool {
+	return rcv._tab.MutateInt32Slot(10, n)
+}
+
+func WalletStart(builder *flatbuffers.Builder) {
+	builder.StartObject(4)
+}
+func WalletAddSegments(builder *flatbuffers.Builder, segments flatbuffers.UOffsetT) {
+	builder.PrependUOffsetTSlot(0, flatbuffers.UOffsetT(segments), 0)
+}
+func WalletStartSegmentsVector(builder *flatbuffers.Builder, numElems int) flatbuffers.UOffsetT {
+	return builder.StartVector(4, numElems, 4)
+}
+func WalletAddAdsForever(builder *flatbuffers.Builder, adsForever bool) {
+	builder.PrependBoolSlot(1, adsForever, false)
+}
+func WalletAddAdsPaidUntilMs(builder *flatbuffers.Builder, adsPaidUntilMs int64) {
+	builder.PrependInt64Slot(2, adsPaidUntilMs, 0)
+}
+func WalletAddHints(builder *flatbuffers.Builder, hints int32) {
+	builder.PrependInt32Slot(3, hints, 0)
+}
+func WalletEnd(builder *flatbuffers.Builder) flatbuffers.UOffsetT {
+	return builder.EndObject()
+}

pkg/fbs/scrabblefb/WalletBuyRequest.go

@@ -0,0 +1,60 @@
+// Code generated by the FlatBuffers compiler. DO NOT EDIT.
+
+package scrabblefb
+
+import (
+	flatbuffers "github.com/google/flatbuffers/go"
+)
+
+type WalletBuyRequest struct {
+	_tab flatbuffers.Table
+}
+
+func GetRootAsWalletBuyRequest(buf []byte, offset flatbuffers.UOffsetT) *WalletBuyRequest {
+	n := flatbuffers.GetUOffsetT(buf[offset:])
+	x := &WalletBuyRequest{}
+	x.Init(buf, n+offset)
+	return x
+}
+
+func FinishWalletBuyRequestBuffer(builder *flatbuffers.Builder, offset flatbuffers.UOffsetT) {
+	builder.Finish(offset)
+}
+
+func GetSizePrefixedRootAsWalletBuyRequest(buf []byte, offset flatbuffers.UOffsetT) *WalletBuyRequest {
+	n := flatbuffers.GetUOffsetT(buf[offset+flatbuffers.SizeUint32:])
+	x := &WalletBuyRequest{}
+	x.Init(buf, n+offset+flatbuffers.SizeUint32)
+	return x
+}
+
+func FinishSizePrefixedWalletBuyRequestBuffer(builder *flatbuffers.Builder, offset flatbuffers.UOffsetT) {
+	builder.FinishSizePrefixed(offset)
+}
+
+func (rcv *WalletBuyRequest) Init(buf []byte, i flatbuffers.UOffsetT) {
+	rcv._tab.Bytes = buf
+	rcv._tab.Pos = i
+}
+
+func (rcv *WalletBuyRequest) Table() flatbuffers.Table {
+	return rcv._tab
+}
+
+func (rcv *WalletBuyRequest) ProductId() []byte {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(4))
+	if o != 0 {
+		return rcv._tab.ByteVector(o + rcv._tab.Pos)
+	}
+	return nil
+}
+
+func WalletBuyRequestStart(builder *flatbuffers.Builder) {
+	builder.StartObject(1)
+}
+func WalletBuyRequestAddProductId(builder *flatbuffers.Builder, productId flatbuffers.UOffsetT) {
+	builder.PrependUOffsetTSlot(0, flatbuffers.UOffsetT(productId), 0)
+}
+func WalletBuyRequestEnd(builder *flatbuffers.Builder) flatbuffers.UOffsetT {
+	return builder.EndObject()
+}

pkg/fbs/scrabblefb/WalletSegment.go

@@ -0,0 +1,90 @@
+// Code generated by the FlatBuffers compiler. DO NOT EDIT.
+
+package scrabblefb
+
+import (
+	flatbuffers "github.com/google/flatbuffers/go"
+)
+
+type WalletSegment struct {
+	_tab flatbuffers.Table
+}
+
+func GetRootAsWalletSegment(buf []byte, offset flatbuffers.UOffsetT) *WalletSegment {
+	n := flatbuffers.GetUOffsetT(buf[offset:])
+	x := &WalletSegment{}
+	x.Init(buf, n+offset)
+	return x
+}
+
+func FinishWalletSegmentBuffer(builder *flatbuffers.Builder, offset flatbuffers.UOffsetT) {
+	builder.Finish(offset)
+}
+
+func GetSizePrefixedRootAsWalletSegment(buf []byte, offset flatbuffers.UOffsetT) *WalletSegment {
+	n := flatbuffers.GetUOffsetT(buf[offset+flatbuffers.SizeUint32:])
+	x := &WalletSegment{}
+	x.Init(buf, n+offset+flatbuffers.SizeUint32)
+	return x
+}
+
+func FinishSizePrefixedWalletSegmentBuffer(builder *flatbuffers.Builder, offset flatbuffers.UOffsetT) {
+	builder.FinishSizePrefixed(offset)
+}
+
+func (rcv *WalletSegment) Init(buf []byte, i flatbuffers.UOffsetT) {
+	rcv._tab.Bytes = buf
+	rcv._tab.Pos = i
+}
+
+func (rcv *WalletSegment) Table() flatbuffers.Table {
+	return rcv._tab
+}
+
+func (rcv *WalletSegment) Source() []byte {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(4))
+	if o != 0 {
+		return rcv._tab.ByteVector(o + rcv._tab.Pos)
+	}
+	return nil
+}
+
+func (rcv *WalletSegment) Chips() int32 {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(6))
+	if o != 0 {
+		return rcv._tab.GetInt32(o + rcv._tab.Pos)
+	}
+	return 0
+}
+
+func (rcv *WalletSegment) MutateChips(n int32) bool {
+	return rcv._tab.MutateInt32Slot(6, n)
+}
+
+func (rcv *WalletSegment) Spendable() bool {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(8))
+	if o != 0 {
+		return rcv._tab.GetBool(o + rcv._tab.Pos)
+	}
+	return false
+}
+
+func (rcv *WalletSegment) MutateSpendable(n bool) bool {
+	return rcv._tab.MutateBoolSlot(8, n)
+}
+
+func WalletSegmentStart(builder *flatbuffers.Builder) {
+	builder.StartObject(3)
+}
+func WalletSegmentAddSource(builder *flatbuffers.Builder, source flatbuffers.UOffsetT) {
+	builder.PrependUOffsetTSlot(0, flatbuffers.UOffsetT(source), 0)
+}
+func WalletSegmentAddChips(builder *flatbuffers.Builder, chips int32) {
+	builder.PrependInt32Slot(1, chips, 0)
+}
+func WalletSegmentAddSpendable(builder *flatbuffers.Builder, spendable bool) {
+	builder.PrependBoolSlot(2, spendable, false)
+}
+func WalletSegmentEnd(builder *flatbuffers.Builder) flatbuffers.UOffsetT {
+	return builder.EndObject()
+}