IRC: edit server settings as a draft, applied under the service lock

The IRC App edited the live config while the IRC task could be reading
it to connect. The App now edits a copy; applyConfig() validates it and
swaps it in under the lock, and the task connects from a snapshot.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

lib/irc/src/irc_config.h

@@ -22,6 +22,21 @@ class IrcConfig {
     std::string nickservPassword;        // otherwise IDENTIFY with NickServ, if set
     std::vector<std::string> autojoin;
 
+    // A copy is a draft the UI can edit freely; copySettingsFrom() applies one.
+    IrcConfig(const IrcConfig&) = default;
+    void copySettingsFrom(const IrcConfig& other) {
+        host = other.host;
+        port = other.port;
+        tls = other.tls;
+        allowSelfSigned = other.allowSelfSigned;
+        pinnedSha256 = other.pinnedSha256;
+        nick = other.nick;
+        saslUser = other.saslUser;
+        saslPassword = other.saslPassword;
+        nickservPassword = other.nickservPassword;
+        autojoin = other.autojoin;
+    }
+
     void load(const std::string& defaultNick);
     std::string save();  // empty on success, otherwise why it was refused
     std::string validate() const;