config: unify configuration with multi-site support

- Remove mock_content setting (working database loop makes it unnecessary)
- Change server.dev_mode to global dev_mode setting for consistency
- Update CLI to use cli.site_id and cli.output for scoped configuration
- Implement database client for CLI enhance command (complete static site loop)
- Update justfile to use INSERTR_DATABASE_PATH environment variable
- Enable multi-site architecture: server is site-agnostic, CLI is site-specific
- Unified insertr.yaml now supports both server and CLI with minimal config

cmd/root.go

@@ -48,7 +48,7 @@ func init() {
 	viper.BindPFlag("database.path", rootCmd.PersistentFlags().Lookup("db"))
 	viper.BindPFlag("api.url", rootCmd.PersistentFlags().Lookup("api-url"))
 	viper.BindPFlag("api.key", rootCmd.PersistentFlags().Lookup("api-key"))
-	viper.BindPFlag("site_id", rootCmd.PersistentFlags().Lookup("site-id"))
+	viper.BindPFlag("cli.site_id", rootCmd.PersistentFlags().Lookup("site-id"))
 
 	rootCmd.AddCommand(enhanceCmd)
 	rootCmd.AddCommand(serveCmd)