Fix BlockRazor gRPC endpoints and set gRPC as default transport

- Add SWQOS_ENDPOINTS_BLOCKRAZOR_GRPC with correct gRPC endpoints
- Add Grpc variant to SwqosTransport enum
- Add get_endpoint_with_transport() method for transport-aware endpoint selection
- Change BlockRazor default: transport=None now uses gRPC (was HTTP)
- Require explicit Some(SwqosTransport::Http) for HTTP fallback

This fixes the issue where BlockRazor was incorrectly using HTTP endpoints
when gRPC was intended. Users can now use gRPC by default or explicitly
specify HTTP transport when needed.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/constants/swqos.rs

@@ -277,6 +277,19 @@ pub const SWQOS_ENDPOINTS_BLOCKRAZOR: [&str; 8] = [
     "http://frankfurt.solana.blockrazor.xyz:443/v2/sendTransaction",
 ];
 
+/// BlockRazor gRPC endpoints. Region order: NewYork, Frankfurt, Amsterdam, SLC, Tokyo, London, LosAngeles, Default.
+/// Port 80 for gRPC protocol. Auth: apikey metadata in gRPC headers.
+pub const SWQOS_ENDPOINTS_BLOCKRAZOR_GRPC: [&str; 8] = [
+    "http://newyork.solana-grpc.blockrazor.xyz:80",
+    "http://frankfurt.solana-grpc.blockrazor.xyz:80",
+    "http://amsterdam.solana-grpc.blockrazor.xyz:80",
+    "http://newyork.solana-grpc.blockrazor.xyz:80",
+    "http://tokyo.solana-grpc.blockrazor.xyz:80",
+    "http://london.solana-grpc.blockrazor.xyz:80",
+    "http://newyork.solana-grpc.blockrazor.xyz:80",
+    "http://frankfurt.solana-grpc.blockrazor.xyz:80",
+];
+
 /// Astralane binary API path (no Base64; use with ?api-key=...&method=sendTransaction|getHealth).
 pub const ASTRALANE_PATH_IRISB: &str = "irisb";