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/XMPP/LumaConnectionStatsModule.swift

@@ -0,0 +1,68 @@
+import Foundation
+import Martin
+
+/// Counts XEP-0198 stanza statistics (sent / acknowledged / received) at the
+/// stream level so the server-details screen can mirror Monal's connection
+/// statistics. Registered as an `XmppStanzaFilter` *before* stream management
+/// so it can also observe the server's `<a h='N'>` acknowledgements.
+final class LumaConnectionStatsModule: XmppModuleBase, XmppModule, XmppStanzaFilter {
+    static let ID = "lumaConnectionStats"
+    static let smNamespace = "urn:xmpp:sm:3"
+
+    let criteria = Criteria.empty()
+    let features: [String] = []
+
+    private let lock = NSLock()
+    private var sent: UInt32 = 0
+    private var received: UInt32 = 0
+    private var acknowledged: UInt32 = 0
+
+    struct Snapshot: Equatable, Sendable {
+        let sent: UInt32
+        let acknowledged: UInt32
+        let received: UInt32
+
+        var unacknowledged: UInt32 {
+            sent > acknowledged ? sent - acknowledged : 0
+        }
+    }
+
+    var snapshot: Snapshot {
+        lock.lock()
+        defer { lock.unlock() }
+        return Snapshot(sent: sent, acknowledged: acknowledged, received: received)
+    }
+
+    func processIncoming(stanza: Stanza) -> Bool {
+        if stanza.xmlns == Self.smNamespace, stanza.name == "a" {
+            if let raw = stanza.getAttribute("h"), let value = UInt32(raw) {
+                lock.lock()
+                acknowledged = value
+                lock.unlock()
+            }
+            // Let StreamManagementModule consume the acknowledgement too.
+            return false
+        }
+        if Self.isCountable(stanza) {
+            lock.lock()
+            received += 1
+            lock.unlock()
+        }
+        return false
+    }
+
+    func processOutgoing(stanza: Stanza) {
+        guard Self.isCountable(stanza) else { return }
+        lock.lock()
+        sent += 1
+        lock.unlock()
+    }
+
+    func process(stanza: Stanza) throws {
+        // Criteria is empty, so this module is never selected by the dispatcher.
+    }
+
+    private static func isCountable(_ stanza: Stanza) -> Bool {
+        stanza.name == "iq" || stanza.name == "message" || stanza.name == "presence"
+    }
+}