Refactor server package: split handlers and routes into separate files

- Move all handler functions to handlers.go
- Move setupRoutes to routes.go
- Clean up server.go to only contain core server logic
- Add missing GetASDetails and GetPrefixDetails to mockStore for tests
- Fix linter errors (magic numbers, unused parameters, blank lines)

internal/server/routes.go

@@ -0,0 +1,41 @@
+package server
+
+import (
+	"time"
+
+	"github.com/go-chi/chi/v5"
+	"github.com/go-chi/chi/v5/middleware"
+)
+
+// setupRoutes configures the HTTP routes
+func (s *Server) setupRoutes() {
+	r := chi.NewRouter()
+
+	// Middleware
+	r.Use(middleware.RequestID)
+	r.Use(middleware.RealIP)
+	r.Use(middleware.Logger)
+	r.Use(middleware.Recoverer)
+	const requestTimeout = 2 * time.Second
+	r.Use(TimeoutMiddleware(requestTimeout))
+	r.Use(JSONResponseMiddleware)
+
+	// Routes
+	r.Get("/", s.handleRoot())
+	r.Get("/status", s.handleStatusHTML())
+	r.Get("/status.json", s.handleStatusJSON())
+
+	// AS and prefix detail pages
+	r.Get("/as/{asn}", s.handleASDetail())
+	r.Get("/prefix/{prefix}", s.handlePrefixDetail())
+
+	// API routes
+	r.Route("/api/v1", func(r chi.Router) {
+		r.Get("/stats", s.handleStats())
+		r.Get("/ip/{ip}", s.handleIPLookup())
+		r.Get("/as/{asn}", s.handleASDetailJSON())
+		r.Get("/prefix/{prefix}", s.handlePrefixDetailJSON())
+	})
+
+	s.router = r
+}