refactor: extract ProxyProvider interface with None and NPM implementations

Replace direct npm.Client usage throughout the codebase with the
proxy.Provider interface, enabling pluggable proxy backends. The
deployer, API layer, and proxy manager now use provider-agnostic
route management (ConfigureRoute/DeleteRoute) instead of NPM-specific
API calls. Adds ProxyRouteID (string) to Instance model and
ProxyProvider setting to Settings, with SQLite migrations for
backward compatibility.

internal/deployer/bluegreen.go

@@ -24,11 +24,11 @@ func (d *Deployer) blueGreenDeploy(
 	settings store.Settings,
 	deployID string,
 	imageTag string,
-) (string, int, string, error) {
+) (string, string, string, error) {
 	// Find existing running instance for this stage (the "blue" instance).
 	existingInstances, err := d.store.GetInstancesByStageID(stage.ID)
 	if err != nil {
-		return "", 0, "", fmt.Errorf("get existing instances: %w", err)
+		return "", "", "", fmt.Errorf("get existing instances: %w", err)
 	}
 
 	var blueInstance *store.Instance
@@ -49,18 +49,18 @@ func (d *Deployer) blueGreenDeploy(
 
 	authConfig, err := d.buildRegistryAuth(project)
 	if err != nil {
-		return "", 0, "", fmt.Errorf("build registry auth: %w", err)
+		return "", "", "", fmt.Errorf("build registry auth: %w", err)
 	}
 
 	if err := d.docker.PullImage(ctx, project.Image, imageTag, authConfig); err != nil {
-		return "", 0, "", fmt.Errorf("pull image: %w", err)
+		return "", "", "", fmt.Errorf("pull image: %w", err)
 	}
 	d.logDeploy(deployID, "Image pulled successfully", "info")
 
 	// Step 2: Ensure network.
 	networkID, err := d.docker.EnsureNetwork(ctx, settings.Network)
 	if err != nil {
-		return "", 0, "", fmt.Errorf("ensure network: %w", err)
+		return "", "", "", fmt.Errorf("ensure network: %w", err)
 	}
 
 	// Step 3: Create and start green container.
@@ -92,7 +92,7 @@ func (d *Deployer) blueGreenDeploy(
 	d.logDeploy(deployID, fmt.Sprintf("Blue-green: creating green container %s", containerName), "info")
 	containerID, err := d.docker.CreateContainer(ctx, containerCfg)
 	if err != nil {
-		return "", 0, instanceID, fmt.Errorf("create container: %w", err)
+		return "", "", instanceID, fmt.Errorf("create container: %w", err)
 	}
 
 	// Create instance record.
@@ -107,7 +107,7 @@ func (d *Deployer) blueGreenDeploy(
 		Port:        project.Port,
 	})
 	if err != nil {
-		return containerID, 0, instanceID, fmt.Errorf("create instance record: %w", err)
+		return containerID, "", instanceID, fmt.Errorf("create instance record: %w", err)
 	}
 	instanceID = inst.ID
 
@@ -117,7 +117,7 @@ func (d *Deployer) blueGreenDeploy(
 
 	d.logDeploy(deployID, fmt.Sprintf("Blue-green: starting green container %s", containerName), "info")
 	if err := d.docker.StartContainer(ctx, containerID); err != nil {
-		return containerID, 0, instanceID, fmt.Errorf("start container: %w", err)
+		return containerID, "", instanceID, fmt.Errorf("start container: %w", err)
 	}
 
 	if err := d.store.UpdateInstanceStatus(instanceID, "running"); err != nil {
@@ -136,25 +136,25 @@ func (d *Deployer) blueGreenDeploy(
 		d.logDeploy(deployID, fmt.Sprintf("Blue-green: health checking green at %s", healthURL), "info")
 
 		if err := d.health.Check(ctx, healthURL); err != nil {
-			return containerID, 0, instanceID, fmt.Errorf("health check green: %w", err)
+			return containerID, "", instanceID, fmt.Errorf("health check green: %w", err)
 		}
 		d.logDeploy(deployID, "Blue-green: green health check passed", "info")
 	}
 
-	// Step 5: Swap NPM proxy to green.
-	var npmProxyID int
+	// Step 5: Swap proxy to green.
+	var proxyRouteID string
 	if stage.EnableProxy {
 		if err := d.store.UpdateDeployStatus(deployID, "configuring_proxy", ""); err != nil {
 			slog.Warn("update deploy status", "error", err)
 		}
 		d.publishDeployStatus(deployID, project.ID, stage.ID, imageTag, "configuring_proxy", "")
 
-		npmProxyID, err = d.configureProxy(ctx, deployID, settings, containerName, project.Port, subdomain)
+		proxyRouteID, err = d.configureProxy(ctx, deployID, settings, containerName, project.Port, subdomain)
 		if err != nil {
-			return containerID, 0, instanceID, fmt.Errorf("configure proxy: %w", err)
+			return containerID, "", instanceID, fmt.Errorf("configure proxy: %w", err)
 		}
 
-		inst.NpmProxyID = npmProxyID
+		inst.ProxyRouteID = proxyRouteID
 		d.logDeploy(deployID, "Blue-green: proxy swapped to green container", "info")
 
 		// Create/update DNS record for the green instance.
@@ -180,5 +180,5 @@ func (d *Deployer) blueGreenDeploy(
 		}
 	}
 
-	return containerID, npmProxyID, instanceID, nil
+	return containerID, proxyRouteID, instanceID, nil
 }