refactor: consolidate config logic into ConfigService

Created centralized ConfigService for configuration management.
Added deprecation comments to ConfigBuilder and AgentBuilder.
Platform-specific defaults centralized in one place.
Removed placeholder ConfigService from agent_lifecycle.go.

aggregator-server/internal/services/agent_builder.go

@@ -11,6 +11,7 @@ import (
 )
 
 // AgentBuilder handles generating embedded agent configurations
+// Deprecated: Configuration logic should use services.ConfigService
 type AgentBuilder struct {
 	buildContext string
 }
@@ -21,6 +22,7 @@ func NewAgentBuilder() *AgentBuilder {
 }
 
 // BuildAgentWithConfig generates agent configuration and prepares signed binary
+// Deprecated: Delegate config generation to services.ConfigService
 func (ab *AgentBuilder) BuildAgentWithConfig(config *AgentConfiguration) (*BuildResult, error) {
 	// Create temporary build directory
 	buildDir, err := os.MkdirTemp("", "agent-build-")