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/README.md b/internal/auth/README.md
index de37010..98d1437 100644
--- a/internal/auth/README.md
+++ b/internal/auth/README.md
@@ -142,11 +142,11 @@ import (
 
 // Create auth options
 authOpts := &auth.InterceptorOptions{
-    Read: auth.OperationAuthConfig{
+    Read: auth.AuthOperationConfig{
         Enabled:      true, // Require auth for reads
         AllowedNpubs: nil,  // Accept any valid signature
     },
-    Write: auth.OperationAuthConfig{
+    Write: auth.AuthOperationConfig{
         Enabled:      true,
         AllowedNpubs: []string{"hex-pubkey-1", "hex-pubkey-2"}, // Whitelist
     },