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/loader.go

@@ -69,9 +69,6 @@ func (l *viperLoader) LoadWithFlags(dbPath, apiURL, apiKey, siteID string) (*Con
 	if apiKey != "" {
 		config.API.Key = apiKey
 	}
-	if siteID != "" {
-		config.CLI.SiteID = siteID
-	}
 
 	return config, validate(config)
 }
@@ -81,10 +78,6 @@ func (l *viperLoader) setDefaults(config *Config) error {
 		config.Database.Path = "./insertr.db"
 	}
 
-	if config.CLI.SiteID == "" {
-		config.CLI.SiteID = "demo"
-	}
-
 	if config.Server.Port == 0 {
 		config.Server.Port = 8080
 	}