🔧 chore: implement JWT configuration with TTL and retention policy

- Add JWTConfig struct with TTL and SecretRetention fields
- Configure default values: TTL=1h, RetentionFactor=2.0, MaxRetention=72h, CleanupInterval=1h
- Add environment variable support (DLC_AUTH_JWT_*)
- Implement getter methods for JWT configuration
- Add comprehensive unit tests for default and custom values
- Update logging to include JWT configuration values
- Fix BDD step implementation issues (duplicate methods, unused imports)
- All BDD tests passing with new JWT configuration

Implements JWT secret retention policy as defined in ADR-0021
Closes #42
Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

pkg/config/config_test.go

@@ -0,0 +1,67 @@
+package config
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestJWTConfigurationDefaults(t *testing.T) {
+	// Test that JWT configuration has proper defaults
+	config, err := LoadConfig()
+	assert.NoError(t, err)
+	assert.NotNil(t, config)
+
+	// Test JWT TTL default
+	expectedTTL := 1 * time.Hour
+	actualTTL := config.GetJWTTTL()
+	assert.Equal(t, expectedTTL, actualTTL, "JWT TTL should default to 1 hour")
+
+	// Test JWT retention factor default
+	expectedFactor := 2.0
+	actualFactor := config.GetJWTSecretRetentionFactor()
+	assert.Equal(t, expectedFactor, actualFactor, "JWT retention factor should default to 2.0")
+
+	// Test JWT max retention default
+	expectedMaxRetention := 72 * time.Hour
+	actualMaxRetention := config.GetJWTSecretMaxRetention()
+	assert.Equal(t, expectedMaxRetention, actualMaxRetention, "JWT max retention should default to 72 hours")
+
+	// Test JWT cleanup interval default
+	expectedCleanupInterval := 1 * time.Hour
+	actualCleanupInterval := config.GetJWTSecretCleanupInterval()
+	assert.Equal(t, expectedCleanupInterval, actualCleanupInterval, "JWT cleanup interval should default to 1 hour")
+}
+
+func TestJWTConfigurationCustomValues(t *testing.T) {
+	// Set custom environment variables
+	t.Setenv("DLC_AUTH_JWT_TTL", "2h")
+	t.Setenv("DLC_AUTH_JWT_SECRET_RETENTION_FACTOR", "3.5")
+	t.Setenv("DLC_AUTH_JWT_SECRET_MAX_RETENTION", "120h")
+	t.Setenv("DLC_AUTH_JWT_SECRET_CLEANUP_INTERVAL", "30m")
+
+	config, err := LoadConfig()
+	assert.NoError(t, err)
+	assert.NotNil(t, config)
+
+	// Test custom JWT TTL
+	expectedTTL := 2 * time.Hour
+	actualTTL := config.GetJWTTTL()
+	assert.Equal(t, expectedTTL, actualTTL, "JWT TTL should be 2 hours from environment variable")
+
+	// Test custom JWT retention factor
+	expectedFactor := 3.5
+	actualFactor := config.GetJWTSecretRetentionFactor()
+	assert.Equal(t, expectedFactor, actualFactor, "JWT retention factor should be 3.5 from environment variable")
+
+	// Test custom JWT max retention
+	expectedMaxRetention := 120 * time.Hour
+	actualMaxRetention := config.GetJWTSecretMaxRetention()
+	assert.Equal(t, expectedMaxRetention, actualMaxRetention, "JWT max retention should be 120 hours from environment variable")
+
+	// Test custom JWT cleanup interval
+	expectedCleanupInterval := 30 * time.Minute
+	actualCleanupInterval := config.GetJWTSecretCleanupInterval()
+	assert.Equal(t, expectedCleanupInterval, actualCleanupInterval, "JWT cleanup interval should be 30 minutes from environment variable")
+}