feat: integrate config system into relay main.go

Add support for loading configuration from YAML file via -config flag.
Wire up auth, rate limiting, and metrics interceptors based on config.

Changes:
- Add -config flag to relay command
- Use config types directly in auth package (AuthOperationConfig)
- Add conversion methods: RateLimitConfig.ToRateLimiter(), MetricsConfig.ToMetrics()
- Add Metrics.Serve() method for prometheus HTTP endpoint
- Update main.go to initialize interceptors from config
- Fix type naming: OperationAuthConfig -> AuthOperationConfig for consistency

Config now supports complete relay setup including auth read/write
allowlists, rate limiting, and prometheus metrics.

1 files changed, 2 insertions, 2 deletions

diff --git a/internal/auth/auth_test.go b/internal/auth/auth_test.go
index 7b0fa13..68c68f5 100644
--- a/internal/auth/auth_test.go
+++ b/internal/auth/auth_test.go
@@ -243,11 +243,11 @@ func TestValidateAuthFromContext(t *testing.T) {
         ctx := metadata.NewIncomingContext(context.Background(), md)
 
         opts := &InterceptorOptions{
-                Read: OperationAuthConfig{
+                Read: AuthOperationConfig{
                         Enabled:      true,
                         AllowedNpubs: nil,
                 },
-                Write: OperationAuthConfig{
+                Write: AuthOperationConfig{
                         Enabled:      true,
                         AllowedNpubs: nil,
                 },