channels: give kicked/banned/promoted/transferred users a real qts so their client applies it

updateChannelParticipant carries the account's qts per the MTProto spec, but
the server always sent Qts: 0, so real clients silently discarded it as a
stale duplicate -- the banned/kicked user's channel never vanished locally
and no correct "removed by admin" message showed, even though the update was
delivered successfully at the transport layer.

Add a durable per-device qts queue (channel_participant_event_queue) sharing
its qts number space with the existing secret-chat queue (one qts sequence
per device, per spec), and use it to stamp a correct, monotonically
increasing qts on the update for every device of the affected user -- for
channel bans/kicks, admin promotion/demotion, and ownership transfer. A
device offline when it happened can now recover the event via
updates.getDifference instead of missing it permanently.

internal/rpc/encrypted_messages.go

@@ -3,6 +3,7 @@ package rpc
 import (
 	"context"
 	"fmt"
+	"sort"
 
 	"github.com/iamxvbaba/td/proto"
 	"github.com/iamxvbaba/td/tg"
@@ -103,6 +104,10 @@ func (r *Router) onMessagesReceivedQueue(ctx context.Context, maxQts int) ([]int
 	if err := r.deps.SecretChats.AckQueue(ctx, deviceKey, maxQts); err != nil {
 		return nil, internalErr()
 	}
+	// Best-effort GC mark for the sibling channel-participant-event queue,
+	// which shares this device's qts sequence; a failure here doesn't affect
+	// correctness (only retention), so it isn't fatal to the RPC.
+	_ = r.deps.SecretChats.AckChannelParticipantEvents(ctx, deviceKey, maxQts)
 	return []int64{}, nil
 }
 
@@ -143,38 +148,84 @@ func (r *Router) deviceEncryptedQts(ctx context.Context) int {
 	return qts
 }
 
-// encryptedDifference 返回当前设备 qts > sinceQts 的连续前缀、推进后的 qts 与是否还有
-// 下一页。存储错误或 qts gap 必须 fail-fast，禁止越过缺口推进客户端水位。
-func (r *Router) encryptedDifference(ctx context.Context, sinceQts int) ([]tg.EncryptedMessageClass, int, bool, error) {
+// encryptedDifference 返回当前设备 qts > sinceQts 的连续前缀（加密消息 +
+// channel 成员关系自通知，二者共用同一设备 qts 序列，按 qts 归并后统一做缺口
+// 检查）、推进后的 qts 与是否还有下一页。存储错误或 qts gap 必须 fail-fast，
+// 禁止越过缺口推进客户端水位。
+func (r *Router) encryptedDifference(ctx context.Context, sinceQts int) ([]tg.EncryptedMessageClass, []tg.UpdateClass, []int64, []int64, int, bool, error) {
 	if r.deps.SecretChats == nil {
-		return nil, sinceQts, false, nil
+		return nil, nil, nil, nil, sinceQts, false, nil
 	}
 	deviceKey, ok := businessAuthKeyIDFrom(ctx)
 	if !ok {
-		return nil, sinceQts, false, nil
+		return nil, nil, nil, nil, sinceQts, false, nil
 	}
 	msgs, err := r.deps.SecretChats.ListNewMessages(ctx, deviceKey, sinceQts, encryptedDifferencePageSize+1)
 	if err != nil {
-		return nil, sinceQts, false, err
+		return nil, nil, nil, nil, sinceQts, false, err
 	}
-	if len(msgs) == 0 {
-		return nil, sinceQts, false, nil
+	participantEvents, err := r.deps.SecretChats.ListChannelParticipantEventsSince(ctx, deviceKey, sinceQts, encryptedDifferencePageSize+1)
+	if err != nil {
+		return nil, nil, nil, nil, sinceQts, false, err
 	}
-	partial := len(msgs) > encryptedDifferencePageSize
-	if partial {
-		msgs = msgs[:encryptedDifferencePageSize]
+	if len(msgs) == 0 && len(participantEvents) == 0 {
+		return nil, nil, nil, nil, sinceQts, false, nil
 	}
-	out := make([]tg.EncryptedMessageClass, 0, len(msgs))
+	items := make([]deviceQtsItem, 0, len(msgs)+len(participantEvents))
+	for i := range msgs {
+		items = append(items, deviceQtsItem{qts: msgs[i].Qts, msg: &msgs[i]})
+	}
+	for i := range participantEvents {
+		items = append(items, deviceQtsItem{qts: participantEvents[i].Qts, participant: &participantEvents[i]})
+	}
+	sort.Slice(items, func(i, j int) bool { return items[i].qts < items[j].qts })
+	partial := len(msgs) > encryptedDifferencePageSize || len(participantEvents) > encryptedDifferencePageSize
+	if len(items) > encryptedDifferencePageSize {
+		items = items[:encryptedDifferencePageSize]
+		partial = true
+	}
+	encMsgs := make([]tg.EncryptedMessageClass, 0, len(items))
+	participantUpdates := make([]tg.UpdateClass, 0, len(items))
+	participantPeerIDs := make([]int64, 0, len(items))
+	participantChannelIDs := make([]int64, 0, len(items))
 	newQts := sinceQts
-	for i, m := range msgs {
+	for i, item := range items {
 		expected := newQts + 1
-		if m.Qts != expected {
-			return nil, sinceQts, false, fmt.Errorf("secret chat qts gap at index %d: got %d want %d", i, m.Qts, expected)
+		if item.qts != expected {
+			return nil, nil, nil, nil, sinceQts, false, fmt.Errorf("device qts gap at index %d: got %d want %d", i, item.qts, expected)
 		}
-		out = append(out, tgEncryptedMessage(m))
-		newQts = m.Qts
+		if item.msg != nil {
+			encMsgs = append(encMsgs, tgEncryptedMessage(*item.msg))
+		} else {
+			ev := item.participant
+			update := &tg.UpdateChannelParticipant{
+				ChannelID: ev.ChannelID,
+				Date:      ev.Date,
+				ActorID:   ev.ActorUserID,
+				UserID:    ev.Participant.UserID,
+				Qts:       ev.Qts,
+			}
+			if ev.Previous.UserID != 0 {
+				update.SetPrevParticipant(tgChannelParticipantForUpdate(ev.ReceiverUserID, ev.Previous))
+			}
+			if ev.Participant.UserID != 0 {
+				update.SetNewParticipant(tgChannelParticipantForUpdate(ev.ReceiverUserID, ev.Participant))
+			}
+			participantUpdates = append(participantUpdates, update, &tg.UpdateChannel{ChannelID: ev.ChannelID})
+			participantPeerIDs = append(participantPeerIDs, ev.ActorUserID, ev.Participant.UserID, ev.Participant.InviterUserID, ev.Previous.UserID, ev.Previous.InviterUserID)
+			participantChannelIDs = append(participantChannelIDs, ev.ChannelID)
+		}
+		newQts = item.qts
 	}
-	return out, newQts, partial, nil
+	return encMsgs, participantUpdates, participantPeerIDs, participantChannelIDs, newQts, partial, nil
+}
+
+// deviceQtsItem is one entry in a device's merged qts stream: either an
+// encrypted message or a channel-participant self-notification, never both.
+type deviceQtsItem struct {
+	qts         int
+	msg         *domain.SecretChatMessage
+	participant *domain.DeviceChannelParticipantEvent
 }
 
 // injectEncryptedMessages 把加密消息与推进后的 qts 注入差分响应（按类型分别写 State /