fix: SweepingProvider shouldn't error when missing DHT (#10975)

* fix: SweepingProvider shouldn't error when missing DHT

* fix: prevent panic when SweepingProvider has no DHT

when SweepingProvider is enabled but no DHT is available (e.g., Routing.Type=none),
the daemon would panic with a nil pointer dereference in ResettableKeystore.ResetCids.

this fix:
- returns NoopProvider when no DHT implementation is available
- skips keystore initialization for NoopProvider to avoid unnecessary operations
- allows nodes to run without DHT when using HTTP-only routing or offline mode

the panic occurred because initKeyStore tried to access a nil keystore when
SweepingProvider returned nil for the keystore parameter. by checking if the
provider is NoopProvider and skipping keystore operations, we avoid the panic
while maintaining correct behavior for all other provider types.

cc #10974 #10975

---------

Co-authored-by: Marcin Rataj <lidel@lidel.org>

core/node/provider.go

@@ -355,13 +355,7 @@ func SweepingProviderOpt(cfg *config.Config) fx.Option {
 			}
 		}
 		if impl == nil {
-			// No DHT available, check if HTTP provider is configured
-			cfg, err := in.Repo.Config()
-			if err == nil && cfg.HasHTTPProviderConfigured() {
-				// HTTP provider is configured, return NoopProvider to allow HTTP-based providing
-				return &NoopProvider{}, keyStore, nil
-			}
-			return &NoopProvider{}, nil, errors.New("provider: no valid DHT available for providing")
+			return &NoopProvider{}, nil, nil
 		}
 
 		var selfAddrsFunc func() []ma.Multiaddr
@@ -403,6 +397,11 @@ func SweepingProviderOpt(cfg *config.Config) fx.Option {
 		KeyProvider provider.KeyChanFunc
 	}
 	initKeyStore := fx.Invoke(func(lc fx.Lifecycle, in keystoreInput) {
+		// Skip keystore initialization for NoopProvider
+		if _, ok := in.Provider.(*NoopProvider); ok {
+			return
+		}
+
 		var (
 			cancel context.CancelFunc
 			done   = make(chan struct{})