feat: add IRC wire protocol listener with shared service layer

Adds a backward-compatible IRC wire protocol listener (RFC 1459/2812)
with a shared service layer used by both IRC and HTTP transports.

- TCP listener on configurable port (default :6667)
- Full IRC protocol: NICK, USER, JOIN, PART, PRIVMSG, MODE, TOPIC, etc.
- Shared service layer (internal/service/) for consistent code paths
- Tier 2 join restrictions (ban, invite-only, key, limit) in service layer
- Ban check on PRIVMSG in service layer
- SetChannelFlag handles +i and +s modes
- Command dispatch via map[string]cmdHandler pattern
- EXPOSE 6667 in Dockerfile
- Service layer unit tests

closes #89

internal/handlers/handlers.go

@@ -17,6 +17,7 @@ import (
 	"git.eeqj.de/sneak/neoirc/internal/healthcheck"
 	"git.eeqj.de/sneak/neoirc/internal/logger"
 	"git.eeqj.de/sneak/neoirc/internal/ratelimit"
+	"git.eeqj.de/sneak/neoirc/internal/service"
 	"git.eeqj.de/sneak/neoirc/internal/stats"
 	"go.uber.org/fx"
 )
@@ -33,6 +34,8 @@ type Params struct {
 	Database    *db.Database
 	Healthcheck *healthcheck.Healthcheck
 	Stats       *stats.Tracker
+	Broker      *broker.Broker
+	Service     *service.Service
 }
 
 const defaultIdleTimeout = 30 * 24 * time.Hour
@@ -48,6 +51,7 @@ type Handlers struct {
 	log             *slog.Logger
 	hc              *healthcheck.Healthcheck
 	broker          *broker.Broker
+	svc             *service.Service
 	hashcashVal     *hashcash.Validator
 	channelHashcash *hashcash.ChannelValidator
 	loginLimiter    *ratelimit.Limiter
@@ -79,7 +83,8 @@ func New(
 		params:          &params,
 		log:             params.Logger.Get(),
 		hc:              params.Healthcheck,
-		broker:          broker.New(),
+		broker:          params.Broker,
+		svc:             params.Service,
 		hashcashVal:     hashcash.NewValidator(resource),
 		channelHashcash: hashcash.NewChannelValidator(),
 		loginLimiter:    ratelimit.New(loginRate, loginBurst),