Percent-decode URL parameters before parsing them (closes #103)

chi matches routes against the escaped path when a request has one and
hands the handlers their URL parameters still percent-encoded. The home
page's lookup form encodes the address it asks for, so every IPv6 lookup
answered 400, as did a comma-separated address list or a prefix that a
client percent-encoded. The router now matches against the decoded path,
so every handler reads its parameters decoded.

Model: opus-5-5

internal/server/routes.go

@@ -12,6 +12,7 @@ func (s *Server) setupRoutes() {
 	r := chi.NewRouter()
 
 	// Middleware
+	r.Use(DecodedPathMiddleware)
 	r.Use(middleware.RequestID)
 	r.Use(middleware.RealIP)
 	r.Use(RequestLoggerMiddleware(s.logger.Logger)) // Structured request logging