admin: add account spam restriction (join/message gate)

Adds a narrower spam sanction alongside the existing account freeze: a
restricted account keeps every existing membership and conversation, but
cannot join new channels/groups (public join or invite link) and cannot
start a new conversation with a non-contact. Reachable both as a standalone
admin action and as a decision on a reported user's moderation case, with
the same idempotent-supersession and appeal wiring freeze already has.

internal/app/dialogs/service.go

@@ -26,6 +26,7 @@ type Service struct {
 	photos           userprojection.ProfilePhotoProvider
 	privacy          userprojection.PrivacyEvaluator
 	freezes          userprojection.AccountFreezeProvider
+	restrictions     userprojection.AccountRestrictionProvider
 	premium          PremiumChecker
 	projector        *userprojection.Projector
 	versions         store.ReadModelVersionStore
@@ -63,6 +64,11 @@ func WithAccountFreezeProvider(p userprojection.AccountFreezeProvider) Option {
 	return func(s *Service) { s.freezes = p }
 }
 
+// WithAccountRestrictionProvider injects the account spam-restriction reader.
+func WithAccountRestrictionProvider(p userprojection.AccountRestrictionProvider) Option {
+	return func(s *Service) { s.restrictions = p }
+}
+
 // WithReadModelVersions enables durable version-token backed peer dialog caching.
 func WithReadModelVersions(v store.ReadModelVersionStore) Option {
 	return func(s *Service) { s.versions = v }
@@ -132,6 +138,7 @@ func (s *Service) rebuildProjector() {
 		userprojection.WithPhotoProvider(s.photos),
 		userprojection.WithPrivacyEvaluator(s.privacy),
 		userprojection.WithAccountFreezeProvider(s.freezes),
+		userprojection.WithAccountRestrictionProvider(s.restrictions),
 	)
 }