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 ./...)

cmd/mciassrv/main.go

@@ -132,11 +132,8 @@ func run(configPath string, logger *slog.Logger) error {
 		}
 
 		grpcSrvImpl := grpcserver.New(database, cfg, privKey, pubKey, masterKey, logger)
-		grpcSrv = grpcSrvImpl.GRPCServer()
-		// Apply TLS to the gRPC server by wrapping options.
-		// We reconstruct the server with TLS credentials since GRPCServer()
-		// returns an already-built server; instead, build with creds directly.
-		// Re-create with TLS option.
+		// Build server directly with TLS credentials. GRPCServerWithCreds builds
+		// the server with transport credentials at construction time per gRPC idiom.
 		grpcSrv = rebuildGRPCServerWithTLS(grpcSrvImpl, grpcTLSCreds)
 
 		grpcListener, err = net.Listen("tcp", cfg.Server.GRPCAddr)