Remove internal/content package and use engine directly

- Eliminate content.Enhancer wrapper around engine.ContentEngine
- Update cmd/enhance.go to call engine.ProcessFile/ProcessDirectory directly
- Update sites/manager.go to use engine.NewContentEngineWithAuth directly
- Remove unused EnhancementConfig and discovery configuration logic
- Simplify enhance command to use input path as site ID
- Remove CLI config dependency from config package

internal/config/config.go

@@ -3,7 +3,6 @@ package config
 type Config struct {
 	Database DatabaseConfig `yaml:"database" mapstructure:"database"`
 	API      APIConfig      `yaml:"api" mapstructure:"api"`
-	CLI      CLIConfig      `yaml:"cli" mapstructure:"cli"`
 	Server   ServerConfig   `yaml:"server" mapstructure:"server"`
 	Auth     AuthConfig     `yaml:"auth" mapstructure:"auth"`
 	Library  LibraryConfig  `yaml:"library" mapstructure:"library"`
@@ -18,10 +17,6 @@ type APIConfig struct {
 	Key string `yaml:"key" mapstructure:"key"`
 }
 
-type CLIConfig struct {
-	SiteID string `yaml:"site_id" mapstructure:"site_id"`
-}
-
 type ServerConfig struct {
 	Port  int          `yaml:"port" mapstructure:"port"`
 	Host  string       `yaml:"host" mapstructure:"host"`
@@ -29,18 +24,10 @@ type ServerConfig struct {
 }
 
 type AuthConfig struct {
-	DevMode      bool                   `yaml:"dev_mode" mapstructure:"dev_mode"`
-	Provider     string                 `yaml:"provider" mapstructure:"provider"`
-	JWTSecret    string                 `yaml:"jwt_secret" mapstructure:"jwt_secret"`
-	OAuthConfigs map[string]OAuthConfig `yaml:"oauth_configs" mapstructure:"oauth_configs"`
-	OIDC         *OIDCConfig            `yaml:"oidc" mapstructure:"oidc"`
-}
-
-type OAuthConfig struct {
-	ClientID     string   `yaml:"client_id" mapstructure:"client_id"`
-	ClientSecret string   `yaml:"client_secret" mapstructure:"client_secret"`
-	RedirectURL  string   `yaml:"redirect_url" mapstructure:"redirect_url"`
-	Scopes       []string `yaml:"scopes" mapstructure:"scopes"`
+	DevMode   bool        `yaml:"dev_mode" mapstructure:"dev_mode"`
+	Provider  string      `yaml:"provider" mapstructure:"provider"`
+	JWTSecret string      `yaml:"jwt_secret" mapstructure:"jwt_secret"`
+	OIDC      *OIDCConfig `yaml:"oidc" mapstructure:"oidc"`
 }
 
 type OIDCConfig struct {