deps: migrate from chi v1 to chi/v5

Migrate all chi imports from github.com/go-chi/chi (v1.5.5) to
github.com/go-chi/chi/v5 (v5.2.1) to resolve GO-2026-4316 open
redirect vulnerability in the RedirectSlashes middleware.

Changes:
- go.mod: replaced chi v1.5.5 with chi/v5 v5.2.1
- Updated import paths in server, routes, middleware, and handlers
- No API changes required (chi/v5 is API-compatible for our usage)

closes #42

internal/handlers/api.go

@@ -12,7 +12,7 @@ import (
 
 	"git.eeqj.de/sneak/neoirc/internal/db"
 	"git.eeqj.de/sneak/neoirc/pkg/irc"
-	"github.com/go-chi/chi"
+	"github.com/go-chi/chi/v5"
 )
 
 var validNickRe = regexp.MustCompile(

internal/middleware/middleware.go

@@ -11,7 +11,7 @@ import (
 	"git.eeqj.de/sneak/neoirc/internal/globals"
 	"git.eeqj.de/sneak/neoirc/internal/logger"
 	basicauth "github.com/99designs/basicauth-go"
-	chimw "github.com/go-chi/chi/middleware"
+	chimw "github.com/go-chi/chi/v5/middleware"
 	"github.com/go-chi/cors"
 	metrics "github.com/slok/go-http-metrics/metrics/prometheus"
 	ghmm "github.com/slok/go-http-metrics/middleware"

internal/server/routes.go

@@ -8,8 +8,8 @@ import (
 	"git.eeqj.de/sneak/neoirc/web"
 
 	sentryhttp "github.com/getsentry/sentry-go/http"
-	"github.com/go-chi/chi"
-	"github.com/go-chi/chi/middleware"
+	"github.com/go-chi/chi/v5"
+	"github.com/go-chi/chi/v5/middleware"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/spf13/viper"
 )

internal/server/server.go

@@ -20,7 +20,7 @@ import (
 	"go.uber.org/fx"
 
 	"github.com/getsentry/sentry-go"
-	"github.com/go-chi/chi"
+	"github.com/go-chi/chi/v5"
 
 	_ "github.com/joho/godotenv/autoload" // loads .env file
 )