refactor(access): migrate config-api-key provider to internal package

- Moved `config-api-key` provider logic from SDK to the internal `config_access` package.
- Updated provider registration and initialization to ensure proper management via `Register` function.
- Removed redundant `config-api-key` documentation, simplifying configuration examples.
- Adjusted related imports and reconciliations for seamless integration with the new structure.

sdk/cliproxy/builder.go

@@ -6,6 +6,7 @@ package cliproxy
 import (
 	"fmt"
 
+	configaccess "github.com/router-for-me/CLIProxyAPI/v6/internal/access/config_access"
 	"github.com/router-for-me/CLIProxyAPI/v6/internal/api"
 	"github.com/router-for-me/CLIProxyAPI/v6/internal/config"
 	sdkaccess "github.com/router-for-me/CLIProxyAPI/v6/sdk/access"
@@ -184,6 +185,8 @@ func (b *Builder) Build() (*Service, error) {
 	if accessManager == nil {
 		accessManager = sdkaccess.NewManager()
 	}
+	configaccess.Register()
+
 	providers, err := sdkaccess.BuildProviders(&b.cfg.SDKConfig)
 	if err != nil {
 		return nil, err