feat: buildServerId + Docker image support for preview deployments

[kopandante]

Problem

Preview deployments fail when using a separate build server (buildServerId != serverId) with a build registry.

Both deployPreviewApplication and rebuildPreviewApplication unconditionally null buildRegistry:

application.buildRegistry = null;

This breaks the entire image delivery pipeline:

1. getBuildCommand() skips uploadImageRemoteCommand() — image never pushed to registry
2. getImageName() returns local name (appName:latest) instead of registry tag
3. getAuthConfig() returns undefined — no auth for Docker Swarm to pull

Regular deployApplication works correctly because it never nulls buildRegistry.

Fix

application.ts: Only null buildRegistry when there's no separate build server:

if (!application.buildServerId || application.buildServerId === application.serverId) {
    application.buildRegistry = null;
}

This preserves the original behavior for same-server deployments while enabling the registry pipeline for external build servers — matching exactly how deployApplication handles it.

builders/index.ts: Fix createService auth in mechanizeDockerContainer:

// Before: auth not extracted by dockerode with single-arg call
await docker.createService(settings);

// After: explicit auth parameter (matches dockerode's two-arg signature)
await docker.createService(settings.authconfig, settings);

service.update() auto-extracts opts.authconfig, but createService() does not when called with a single argument — this is an existing dockerode inconsistency.

Test plan

• Preview deployment with buildServerId different from serverId and buildRegistry configured
• Preview deployment without build server (same-server) — should behave as before
• Regular (non-preview) deployment — no changes in code path

[greptile-apps]

_{5 files reviewed, 1 comment}

_{Edit Code Review Agent Settings | Greptile}

[greptile-apps]

still passing application.serverId instead of buildServerId to cleanup old logs

Suggested change

	await removeLastTenDeployments(
	deployment.previewDeploymentId,
	"previewDeployment",
	previewDeployment?.application?.serverId,
	);
	await removeLastTenDeployments(
	deployment.previewDeploymentId,
	"previewDeployment",
	buildServerId,
	);