fix: increase retry defaults to 5 retries and 60s max delay

Per sneak's feedback: DefaultMaxRetries 3→5, DefaultMaxDelay 10s→60s.

closes #62

internal/notify/retry.go

@@ -11,14 +11,14 @@ import (
 const (
 	// DefaultMaxRetries is the number of additional attempts
 	// after the first failure.
-	DefaultMaxRetries = 3
+	DefaultMaxRetries = 5
 
 	// DefaultBaseDelay is the initial delay before the first
 	// retry attempt.
 	DefaultBaseDelay = 1 * time.Second
 
 	// DefaultMaxDelay caps the computed backoff delay.
-	DefaultMaxDelay = 10 * time.Second
+	DefaultMaxDelay = 60 * time.Second
 
 	// backoffMultiplier is the exponential growth factor.
 	backoffMultiplier = 2