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/ServerInformation.swift

@@ -0,0 +1,156 @@
+import Foundation
+
+/// Snapshot of everything the "server details" screen shows, modelled after
+/// Monal's `ServerDetails`: server software (XEP-0092), disco#info identities
+/// and features (XEP-0030), conference (MUC) services, STUN/TURN services
+/// (XEP-0215) and a few connection-level capability flags.
+struct ServerInformation: Equatable, Sendable {
+    enum CapabilityStatus: Equatable, Sendable {
+        case success, normal, warning, error
+    }
+
+    struct Software: Equatable, Sendable {
+        let name: String?
+        let version: String?
+        let os: String?
+    }
+
+    struct Identity: Equatable, Sendable, Identifiable {
+        let category: String
+        let type: String
+        let name: String?
+
+        var id: String { "\(category)/\(type)" }
+
+        var title: String { "\(category) / \(type)" }
+    }
+
+    struct ConferenceServer: Equatable, Sendable, Identifiable {
+        let jid: String
+        let name: String?
+        let type: String
+        let category: String
+
+        var id: String { jid }
+    }
+
+    struct ExternalService: Equatable, Sendable, Identifiable {
+        let type: String
+        let host: String
+        let port: UInt16?
+        let transport: String?
+
+        var id: String { "\(type)|\(host)|\(port.map(String.init) ?? "")" }
+    }
+
+    struct ConnectionStats: Equatable, Sendable {
+        let lastLogin: Date?
+        let smacksSessionEstablished: Date?
+        let sent: UInt32
+        let acknowledged: UInt32
+        let received: UInt32
+
+        var unacknowledged: UInt32 {
+            sent > acknowledged ? sent - acknowledged : 0
+        }
+    }
+
+    struct Capability: Equatable, Sendable, Identifiable {
+        let title: String
+        let detail: String
+        let status: CapabilityStatus
+
+        var id: String { title }
+    }
+
+    let serverDomain: String
+    let software: Software
+    let identities: [Identity]
+    let serverFeatures: [String]
+    let accountFeatures: [String]
+    let conferenceServers: [ConferenceServer]
+    let externalServices: [ExternalService]
+    let connectionStats: ConnectionStats
+    let saslMethods: [String]
+    let supportsStreamManagement: Bool
+    let supportsCarbons: Bool
+    let supportsClientState: Bool
+    let supportsHTTPUpload: Bool
+    let supportsRosterVersioning: Bool
+    let supportsRosterPreApproval: Bool
+
+    /// The curated XEP list Monal shows, with a status derived from the server
+    /// and account disco features plus the connection-level flags.
+    var capabilities: [Capability] {
+        let server = Set(serverFeatures)
+        let account = Set(accountFeatures)
+        let supportsPubSub = account.contains { $0.hasPrefix("http://jabber.org/protocol/pubsub") }
+        return [
+            Capability(
+                title: "XEP-0163 Personal Eventing Protocol",
+                detail: "Публикация событий состояния аккаунта (аватары, статусы) через publish-subscribe.",
+                status: supportsPubSub ? .success : .error
+            ),
+            Capability(
+                title: "XEP-0191 Blocking Command",
+                detail: "Расширение XMPP для блокировки контактов.",
+                status: server.contains("urn:xmpp:blocking") ? .success : .error
+            ),
+            Capability(
+                title: "XEP-0198 Stream Management",
+                detail: "Возобновление потока при обрыве соединения — быстрее переподключение и экономия заряда.",
+                status: supportsStreamManagement ? .success : .error
+            ),
+            Capability(
+                title: "XEP-0199 XMPP Ping",
+                detail: "Пинг уровня приложения поверх XML-потока.",
+                status: server.contains("urn:xmpp:ping") ? .success : .error
+            ),
+            Capability(
+                title: "XEP-0215 External Service Discovery",
+                detail: "Обнаружение внешних сервисов (STUN/TURN) для аудио- и видеозвонков.",
+                status: server.contains("urn:xmpp:extdisco:2") ? .success : .error
+            ),
+            Capability(
+                title: "XEP-0237 Roster Versioning",
+                detail: "Версионирование ростера, чтобы сервер не отправлял его повторно, если он не менялся.",
+                status: supportsRosterVersioning ? .success : .error
+            ),
+            Capability(
+                title: "XEP-0280 Message Carbons",
+                detail: "Синхронизация сообщений между всеми вашими устройствами.",
+                status: supportsCarbons ? .success : .error
+            ),
+            Capability(
+                title: "XEP-0313 Message Archive Management",
+                detail: "Доступ к архиву сообщений на сервере.",
+                status: account.contains("urn:xmpp:mam:2") ? .success : .error
+            ),
+            Capability(
+                title: "XEP-0352 Client State Indication",
+                detail: "Указывает, активно ли устройство. Экономит заряд.",
+                status: supportsClientState ? .success : .error
+            ),
+            Capability(
+                title: "XEP-0357 Push Notifications",
+                detail: "Push-уведомления через Apple даже когда приложение выгружено.",
+                status: account.contains("urn:xmpp:push:0") ? .success : .error
+            ),
+            Capability(
+                title: "XEP-0363 HTTP File Upload",
+                detail: "Загрузка файлов на сервер для обмена с собеседниками.",
+                status: supportsHTTPUpload ? .success : .error
+            ),
+            Capability(
+                title: "XEP-0379 Pre-Authenticated Roster Subscription",
+                detail: "Ссылки для предварительно аутентифицированной подписки на присутствие.",
+                status: supportsRosterPreApproval ? .success : .error
+            ),
+            Capability(
+                title: "XEP-0474 SASL SCRAM Downgrade Protection",
+                detail: "Защита SASL/SASL2-рукопожатия от понижения метода и channel-binding. Определяется во время SCRAM-аутентификации, а не рекламируется статически.",
+                status: .normal
+            ),
+        ]
+    }
+}