add server info screen, connection stats, and emoji picker

Server information (Monal-style):
- Add ServerInformation model and ServerInfoView reachable from
  Settings,
  showing server software (XEP-0092), disco#info identities and
  features,
  conference (MUC) services via disco#items, and STUN/TURN via XEP-0215.
- Add a curated XEP capability list with per-XEP success/error status
  derived
  from server/account disco features and connection flags.
- Detect PEP (0163) from account disco pubsub#* features, HTTP Upload
  (0363)
  from the main domain plus its components, and add Roster Versioning
  (0237),
  Pre-Authenticated Roster Subscription (0379), and SASL SCRAM Downgrade
  Protection (0474, neutral because Martin does not expose SSDP).

Connection statistics:
- Add LumaConnectionStatsModule, an XmppStanzaFilter registered before
  stream
  management, to count sent / acknowledged / received stanzas.
- Track last login and SMACKS session timestamps, and read SASL
  mechanisms
  and Client State Indication from the raw stream features.

MAM / OMEMO handling:
- Prefer a plaintext <body> fallback when OMEMO decryption fails instead
  of
  showing "failed to decrypt".
- Keep the optimistic text of our own outgoing message when its echo
  cannot
  be decrypted back, instead of replacing it with a placeholder.

Emoji picker:
- Add EmojiCatalog and a cross-platform EmojiPickerView.
- Open the picker for reactions (replacing the static quick list) and
  from
  the composer's smiley button, inserting the chosen emoji into the
  draft.

Sources/Shared/Models/AppModel.swift

@@ -41,6 +41,7 @@ final class AppModel: ObservableObject {
     @Published var selectedConversationID: String?
     @Published private(set) var isOMEMOReady = false
     @Published private(set) var ownFingerprint: String?
+    @Published private(set) var serverInformation: ServerInformation?
     @Published private(set) var isArchiveSyncing = false
     @Published private(set) var isLoadingOlderHistory = false
     @Published private(set) var hasMoreOlderHistory = true
@@ -1621,6 +1622,15 @@ final class AppModel: ObservableObject {
         objectWillChange.send()
     }
 
+    func refreshServerInformation() async {
+        do {
+            serverInformation = try await xmpp.fetchServerInformation()
+        } catch {
+            // The screen shows its own error state; keep any previously loaded
+            // snapshot rather than clearing it on a transient refresh failure.
+        }
+    }
+
     func clearError() {
         errorMessage = nil
     }
@@ -2521,6 +2531,25 @@ final class AppModel: ObservableObject {
                 merged.security = previous.security
                 merged.encryptionFingerprint = previous.encryptionFingerprint
             }
+            if message.security == .decryptionFailed,
+               previous.security != .decryptionFailed,
+               !previous.body.isEmpty
+            {
+                // Our own outgoing message was rendered optimistically with the
+                // text the user typed. Its server echo (carbon or MAM) cannot
+                // be decrypted back (no encrypt-to-self key, or a consumed
+                // session), so keep the original content instead of replacing
+                // it with a "failed to decrypt" placeholder.
+                merged.body = previous.body
+                merged.security = previous.security
+                merged.encryptionFingerprint = previous.encryptionFingerprint
+                merged.kind = previous.kind
+                merged.remoteAttachmentURL = previous.remoteAttachmentURL
+                merged.localFilename = previous.localFilename
+                merged.mimeType = previous.mimeType
+                merged.duration = previous.duration
+                merged.byteCount = previous.byteCount
+            }
             messages[index] = merged
             if let stanzaID = merged.stanzaID {
                 messageIndexByStanzaKey[