feat: add IRC wire protocol listener with shared service layer

Add a traditional IRC wire protocol listener (RFC 1459/2812) on
configurable port (default :6667), sharing business logic with
the HTTP API via a new service layer.

- IRC listener: NICK, USER, PASS, JOIN, PART, PRIVMSG, NOTICE,
  TOPIC, MODE, KICK, QUIT, NAMES, LIST, WHOIS, WHO, AWAY, OPER,
  INVITE, LUSERS, MOTD, PING/PONG, CAP
- Service layer: shared logic for both transports including
  channel join (with Tier 2 checks: ban/invite/key/limit),
  message send (with ban + moderation checks), nick change,
  topic, kick, mode, quit broadcast, away, oper, invite
- BroadcastQuit uses FanOut pattern (one insert, N enqueues)
- HTTP handlers delegate to service for all command logic
- Tier 2 mode operations (+b/+i/+s/+k/+l) use service methods

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/handlers/api_test.go

@@ -18,6 +18,7 @@ import (
 	"testing"
 	"time"
 
+	"git.eeqj.de/sneak/neoirc/internal/broker"
 	"git.eeqj.de/sneak/neoirc/internal/config"
 	"git.eeqj.de/sneak/neoirc/internal/db"
 	"git.eeqj.de/sneak/neoirc/internal/globals"
@@ -27,6 +28,7 @@ import (
 	"git.eeqj.de/sneak/neoirc/internal/logger"
 	"git.eeqj.de/sneak/neoirc/internal/middleware"
 	"git.eeqj.de/sneak/neoirc/internal/server"
+	"git.eeqj.de/sneak/neoirc/internal/service"
 	"git.eeqj.de/sneak/neoirc/internal/stats"
 	"go.uber.org/fx"
 	"go.uber.org/fx/fxtest"
@@ -206,6 +208,14 @@ func newTestHandlers(
 	hcheck *healthcheck.Healthcheck,
 	tracker *stats.Tracker,
 ) (*handlers.Handlers, error) {
+	brk := broker.New()
+	svc := service.New(service.Params{ //nolint:exhaustruct
+		Logger:   log,
+		Config:   cfg,
+		Database: database,
+		Broker:   brk,
+	})
+
 	hdlr, err := handlers.New(lifecycle, handlers.Params{ //nolint:exhaustruct
 		Logger:      log,
 		Globals:     globs,
@@ -213,6 +223,8 @@ func newTestHandlers(
 		Database:    database,
 		Healthcheck: hcheck,
 		Stats:       tracker,
+		Broker:      brk,
+		Service:     svc,
 	})
 	if err != nil {
 		return nil, fmt.Errorf("test handlers: %w", err)