fix(drift): resolve image tags via effective compose model (#1574)

Drift compared raw compose YAML to runtime, so ${VAR:-default} image
expressions false-positive as image-mismatch. Source the declared side
from docker compose config instead, matching deploy-time resolution.

Fixes #1572

backend/src/helpers/effectiveToDeclaredCompose.ts

@@ -0,0 +1,52 @@
+import type { EffectiveModel, EffResource } from '../services/preflight/effectiveModel';
+import type { DeclaredCompose, DeclaredPort, DeclaredResource, DeclaredService } from './composeDependencyParse';
+
+/** Map one rendered network/volume entry to the declared shape drift expects. */
+function toDeclaredResource(key: string, res: EffResource, projectName: string): DeclaredResource {
+  const defaultName = res.external ? key : `${projectName}_${key}`;
+  if (res.name === defaultName) {
+    return { external: res.external };
+  }
+  return { external: res.external, name: res.name };
+}
+
+function toDeclaredResourceRecord(
+  resources: Record<string, EffResource>,
+  projectName: string,
+): Record<string, DeclaredResource> {
+  return Object.fromEntries(
+    Object.entries(resources).map(([key, res]) => [key, toDeclaredResource(key, res, projectName)]),
+  );
+}
+
+/**
+ * Convert a fully-rendered effective model (`docker compose config`) into the
+ * {@link DeclaredCompose} shape consumed by the spatial drift engine. Variable
+ * substitution, defaults, multi-file merge, and profile filtering are already
+ * applied upstream.
+ */
+export function declaredFromEffectiveModel(model: EffectiveModel): DeclaredCompose {
+  const { projectName } = model;
+  const services: DeclaredService[] = model.services.map((s) => ({
+    name: s.name,
+    dependsOn: [],
+    networks: s.networks.map((n) => n.key),
+    volumes: [],
+    ports: s.ports.map(
+      (p): DeclaredPort => ({
+        hostIp: p.hostIp,
+        publishedPort: p.startPort,
+        protocol: p.protocol,
+      }),
+    ),
+    image: s.image,
+    networkMode: s.networkMode,
+  }));
+
+  return {
+    services,
+    networks: toDeclaredResourceRecord(model.networks, projectName),
+    volumes: toDeclaredResourceRecord(model.volumes, projectName),
+    projectName,
+  };
+}