M1 step 4b: IRC Service on the device; 8-bit frame buffer

- IrcService: networking on its own task, TLS with the built-in CA
  bundle (or trust-on-first-use pinning when self-signed is allowed),
  plain TCP when TLS is off; connects only while Wi-Fi is Connected,
  marks pauses for Monitoring, reconnects with backoff, pings a quiet
  server, writes Logs, raises Notifications for Mentions
- Session: forget /quit once disconnected (it was handled every loop);
  the server Buffer never counts as unread (MOTD showed as [4])
- Status Bar: unread count
- Frame buffer 16 -> 8-bit colour (M1 Q46): min free heap with IRC on
  TLS went from 51 KB to 79 KB
- Serial: irc start / say / dump

Verified on the device against irc.libera.chat:6697: certificate
checked, joined #roro9stack-test, sent a message, quit cleanly.

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

src/ui/widgets.cpp

@@ -29,6 +29,7 @@ void statusBar(Canvas& c, const StatusInfo& info) {
         x -= c.textWidth(text.c_str()) + 6;
     };
     right(info.clock, kText);
+    if (info.unread > 0) right("[" + std::to_string(info.unread) + "]", kMessage);
     if (info.batteryPercent >= 0)
         right(std::to_string(info.batteryPercent) + "%", info.batteryPercent <= 15 ? kWarning : kText);
     if (info.sdPresent) right("SD", info.sdLevel >= 80 ? kWarning : kMuted);