Fix all golangci-lint warnings

- errorlint: use errors.Is for db.ErrNotFound comparisons
  in accountservice.go, credentialservice.go, tokenservice.go
- gofmt/goimports: move mciasv1 alias into internal import group
  in auth.go, credentialservice.go, grpcserver.go, grpcserver_test.go
- gosec G115: add nolint annotation on int32 port conversions
  in mciasgrpcctl/main.go and credentialservice.go (port validated
  as [1,65535] on input; overflow not reachable)
- govet fieldalignment: reorder Server, grpcRateLimiter,
  grpcRateLimitEntry, testEnv structs to reduce GC bitmap size
  (96 -> 80 pointer bytes each)
- ineffassign: remove intermediate grpcSrv = GRPCServer() call
  in cmd/mciassrv/main.go (immediately overwritten by TLS build)
- staticcheck SA9003: replace empty if-body with _ = Serve(lis)
  in grpcserver_test.go
0 golangci-lint issues; 137 tests pass (go test -race ./...)

internal/grpcserver/grpcserver_test.go

@@ -22,12 +22,12 @@ import (
 	"google.golang.org/grpc/status"
 	"google.golang.org/grpc/test/bufconn"
 
+	mciasv1 "git.wntrmute.dev/kyle/mcias/gen/mcias/v1"
 	"git.wntrmute.dev/kyle/mcias/internal/auth"
 	"git.wntrmute.dev/kyle/mcias/internal/config"
 	"git.wntrmute.dev/kyle/mcias/internal/db"
 	"git.wntrmute.dev/kyle/mcias/internal/model"
 	"git.wntrmute.dev/kyle/mcias/internal/token"
-	mciasv1 "git.wntrmute.dev/kyle/mcias/gen/mcias/v1"
 )
 
 const (
@@ -38,11 +38,11 @@ const (
 // testEnv holds all resources for a single test's gRPC server.
 type testEnv struct {
 	db        *db.DB
+	cfg       *config.Config
+	conn      *grpc.ClientConn
 	priv      ed25519.PrivateKey
 	pub       ed25519.PublicKey
 	masterKey []byte
-	cfg       *config.Config
-	conn      *grpc.ClientConn
 }
 
 // newTestEnv spins up an in-process gRPC server using bufconn and returns
@@ -76,9 +76,7 @@ func newTestEnv(t *testing.T) *testEnv {
 
 	lis := bufconn.Listen(bufConnSize)
 	go func() {
-		if err := grpcSrv.Serve(lis); err != nil {
-			// Serve returns when the listener is closed; ignore that error.
-		}
+		_ = grpcSrv.Serve(lis) // returns on listener close; error ignored
 	}()
 
 	conn, err := grpc.NewClient(