Phase 18: image prune (dangling/unused), local + agent (0.24.0)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/services/image_service.py

@@ -45,3 +45,17 @@ def list_images() -> list[dict]:
             )
     result.sort(key=lambda r: r["tag"])
     return result
+
+
+def prune_images(all_unused: bool = False) -> dict:
+    """Remove unused images. By default only dangling (untagged) images are
+    removed; ``all_unused=True`` removes every image not referenced by a
+    container (``docker image prune -a``)."""
+    client = get_client()
+    # dangling=false tells the engine to also consider tagged-but-unused images.
+    filters = {"dangling": False} if all_unused else {"dangling": True}
+    result = safe_call(client.images.prune, filters=filters)
+    return {
+        "ImagesDeleted": result.get("ImagesDeleted") or [],
+        "SpaceReclaimed": result.get("SpaceReclaimed", 0),
+    }