M1 step 4a: IRC protocol core (host-tested)

lib/irc: IrcMessage parse/serialize, base64, ReconnectPolicy
(5 s .. 5 min), IrcConfig (validated, persisted) and IrcSession:
registration with SASL PLAIN or NickServ, nick fallback, PING, Buffers
capped at 50 lines with unread counts, Mentions, CTCP ACTION/VERSION,
topics, /names on request only, others' join/part/quit hidden, user
commands, and rejoining after a pause. No networking: the session
returns lines to send, Log entries and Notifications.

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

lib/irc/src/irc_config.h

@@ -0,0 +1,36 @@
+#pragma once
+
+#include <string>
+#include <vector>
+
+#include "key_value_store.h"
+
+namespace roro {
+
+// The one IRC server the IRC Service connects to, persisted in internal flash.
+class IrcConfig {
+   public:
+    explicit IrcConfig(KeyValueStore& store) : store_(store) {}
+
+    std::string host = "irc.libera.chat";
+    int port = 6697;
+    bool tls = true;
+    bool allowSelfSigned = false;  // pin the certificate on first use instead of checking a CA
+    std::string pinnedSha256;      // hex fingerprint once pinned
+    std::string nick;
+    std::string saslUser, saslPassword;  // SASL PLAIN when both are set
+    std::string nickservPassword;        // otherwise IDENTIFY with NickServ, if set
+    std::vector<std::string> autojoin;
+
+    void load(const std::string& defaultNick);
+    std::string save();  // empty on success, otherwise why it was refused
+    std::string validate() const;
+
+    static std::vector<std::string> parseChannels(const std::string& text);
+    static std::string formatChannels(const std::vector<std::string>& channels);
+
+   private:
+    KeyValueStore& store_;
+};
+
+}  // namespace roro