Remove concurrency config

Inference engines handle this now.

internal/config/config.go

@@ -20,9 +20,6 @@ type Config struct {
 	// Address is the host:port to listen on.
 	Address string `yaml:"address"`
 
-	// Concurrency is the number of concurrent requests to allow.
-	// Defaults to 1.
-	Concurrency int `yaml:"concurrency"`
 	// ShutdownTimeout is the maximum time to wait for graceful shutdown.
 	// Defaults to "30s".
 	ShutdownTimeout string `yaml:"shutdown_timeout"`
@@ -42,9 +39,6 @@ type Config struct {
 // ApplyDefaults sets default values for optional configuration fields.
 // Called automatically by Load before validation.
 func (cfg *Config) ApplyDefaults() {
-	if cfg.Concurrency == 0 {
-		cfg.Concurrency = 1
-	}
 	if cfg.ShutdownTimeout == "" {
 		cfg.ShutdownTimeout = "30s"
 	}