Stage 11: account linking & merge (email + Telegram Login Widget)

Link an email (confirm-code) or Telegram (web Login Widget) to the current
account; if the identity already has its own account, merge the two into the
one in use (the current account is primary, except a guest initiator whose
durable counterpart wins). The merge runs in one transaction
(internal/accountmerge): stats + hint wallet summed, paid_account ORed,
identities/games/chat/complaints transferred, friends/blocks de-duplicated,
the secondary kept as a merged_into tombstone so a shared finished game's
no-cascade FKs hold; a shared active game blocks the merge.

- migration 00009: accounts.paid_account, merged_into, merged_at (+ jetgen)
- internal/link orchestrator; session.RevokeAllForAccount on merge
- connector ValidateLoginWidget RPC + loginwidget HMAC validator
- edge ops link.email.request/confirm/merge, link.telegram.confirm/merge;
  supersedes the Stage 8 email.bind.* surface (request never reveals 'taken'
  before the code is verified, so a probe cannot enumerate addresses)
- UI Profile link section + irreversible-merge dialog; Telegram web sign-in
- focused regression tests (merge core, guest inversion, active-game refusal,
  finished-shared-game kept), gateway transcode + connector + UI codec/e2e
- docs: PLAN, ARCHITECTURE 3/4/9, FUNCTIONAL(+ru), module READMEs

gateway/internal/transcode/transcode_social.go

@@ -28,8 +28,6 @@ const (
 	MsgInvitationDecline = "invitation.decline"
 	MsgInvitationCancel  = "invitation.cancel"
 	MsgProfileUpdate     = "profile.update"
-	MsgEmailBindReq      = "email.bind.request"
-	MsgEmailBindConfirm  = "email.bind.confirm"
 	MsgStatsGet          = "stats.get"
 	MsgGameGCG           = "game.gcg"
 )
@@ -54,8 +52,6 @@ func registerStage8(r *Registry, backend *backendclient.Client) {
 	r.ops[MsgInvitationDecline] = Op{Handler: invitationRespondHandler(backend, false), Auth: true}
 	r.ops[MsgInvitationCancel] = Op{Handler: invitationCancelHandler(backend), Auth: true}
 	r.ops[MsgProfileUpdate] = Op{Handler: profileUpdateHandler(backend), Auth: true}
-	r.ops[MsgEmailBindReq] = Op{Handler: emailBindRequestHandler(backend), Auth: true, Email: true}
-	r.ops[MsgEmailBindConfirm] = Op{Handler: emailBindConfirmHandler(backend), Auth: true, Email: true}
 	r.ops[MsgStatsGet] = Op{Handler: statsHandler(backend), Auth: true}
 	r.ops[MsgGameGCG] = Op{Handler: gcgHandler(backend), Auth: true}
 }
@@ -250,27 +246,6 @@ func profileUpdateHandler(backend *backendclient.Client) Handler {
 	}
 }
 
-func emailBindRequestHandler(backend *backendclient.Client) Handler {
-	return func(ctx context.Context, req Request) ([]byte, error) {
-		in := fb.GetRootAsEmailBindRequest(req.Payload, 0)
-		if err := backend.EmailBindRequest(ctx, req.UserID, string(in.Email())); err != nil {
-			return nil, err
-		}
-		return encodeAck(true), nil
-	}
-}
-
-func emailBindConfirmHandler(backend *backendclient.Client) Handler {
-	return func(ctx context.Context, req Request) ([]byte, error) {
-		in := fb.GetRootAsEmailConfirmRequest(req.Payload, 0)
-		out, err := backend.EmailBindConfirm(ctx, req.UserID, string(in.Email()), string(in.Code()))
-		if err != nil {
-			return nil, err
-		}
-		return encodeProfile(out), nil
-	}
-}
-
 func statsHandler(backend *backendclient.Client) Handler {
 	return func(ctx context.Context, req Request) ([]byte, error) {
 		res, err := backend.Stats(ctx, req.UserID)