core: forward compatible support for owners/admins/moderations deleting channel and public group messages without limitations (#6962)

* plan: delete channel messages

* core: allow deletion of own messages in public groups in channels to moderators-owners

---------

Co-authored-by: Evgeny @ SimpleX Chat <259188159+evgeny-simplex@users.noreply.github.com>

plans/2026-05-11-channel-owner-unlimited-delete.md

@@ -0,0 +1,36 @@
+# Channel owner unlimited delete
+
+## Problem
+
+Channel owners cannot delete content older than 24 hours. The limit makes sense in p2p groups (no authority, each member holds independent copy). In channels, the owner is the authority - their content, their right to remove it.
+
+## Changes
+
+### PR 1 - subscriber side (release first)
+
+**Subscriber.hs:2168** - `rcvItemDeletable` check on `CIGroupRcv` path. When the sender has editorial role in a channel (`useRelays' gInfo && memberRole' mem >= GRModerator`), skip the time check.
+
+**Subscriber.hs:1912** - `rcvItemDeletable` itself doesn't need to change - the caller skips it.
+
+### PR 2 - owner side (release after subscribers update)
+
+**Messages.hs:535** - `deletable'` returns `True` without time check when the item is in a channel where the user's role >= GRModerator. Needs group context threaded in, or a separate check at the call site.
+
+**Commands.hs:790** - `assertDeletable` for `APIDeleteChatItem` - skip time check for channel editorial roles (>= GRModerator).
+
+**UI (iOS + Kotlin)** - remove the "delete for me / delete for everyone" question for channel owners/admins/moderators. In channels, editorial deletion is always for everyone. The "delete for me only" option makes no sense for a publication.
+
+### Strings
+
+`group_members_can_delete_channel` - "(24 hours)" should note that this limit applies to subscribers, not owners. Owners can delete at any time.
+
+Other `(24 hours)` strings are for direct chats and p2p groups - unchanged.
+
+### Scope
+
+In channels, owners/admins/moderators (role >= GRModerator) get unlimited delete of their own content - they are the editorial team. Members/subscribers stay on 24-hour limit. Moderation of others' content is already unlimited (separate code path, no time check).
+
+## Release order
+
+1. PR 1 ships. Old owners can't send old deletions yet, so nothing changes for subscribers. New subscribers are ready.
+2. PR 2 ships. Owners can now delete old content. New subscribers honor it. Old subscribers silently ignore (message stays - acceptable degradation, not an error after PR 1).

src/Simplex/Chat/Library/Subscriber.hs

@@ -2165,7 +2165,7 @@ processAgentMessageConn vr user@User {userId} corrId agentConnId agentMessage =
             in case sndMemberId_ of
               -- regular deletion
               Nothing
-                | sameMemberId memberId mem && rcvItemDeletable ci brokerTs ->
+                | sameMemberId memberId mem && (publicGroupItemDeletable mem || rcvItemDeletable ci brokerTs) ->
                     delete cci False Nothing
                 | otherwise ->
                     messageError "x.msg.del: member attempted invalid message delete" $> Nothing
@@ -2201,6 +2201,7 @@ processAgentMessageConn vr user@User {userId} corrId agentConnId agentMessage =
             messageError ("x.msg.del: channel message not found, " <> tshow e) $> Nothing
       where
         isOwner = maybe True (\m -> memberRole' m == GROwner) m_
+        publicGroupItemDeletable mem = useRelays' gInfo && memberRole' mem >= GRModerator
         RcvMessage {msgId} = rcvMsg
         findItem = do
           let tryMemberLookup mId =