Automate host preparation and speed up game file downloads

src/lib/ui/components/DeployServerDialog.svelte

@@ -23,7 +23,7 @@
     let maps = $derived(catalogs[game]);
     let selectedBlueprint = $derived(blueprints.find(b => b.id === blueprintId));
     let preview = $state<LaunchPreview | null>(null);
-    let hostSelection = $state<NativeDeploymentSelection>({ hostId: '', libraryIds: {}, image: 'ghcr.io/ayymoss/plutainer:latest' });
+    let hostSelection = $state<NativeDeploymentSelection>({ hostId: '', libraryIds: {}, image: '' });
     let hostReady = $state(false);
     let plutoKey = $state('');
     let busy = $state(false);
@@ -54,7 +54,7 @@
         blueprintId = initialBlueprintId;
         game = initialGame;
         mapSlug = initialMapSlug;
-        hostSelection = { hostId: '', libraryIds: {}, image: 'ghcr.io/ayymoss/plutainer:latest' }; hostReady = false;
+        hostSelection = { hostId: '', libraryIds: {}, image: '' }; hostReady = false;
         try {
             const [mapRes, blueprintRes] = await Promise.all([fetch('/api/maps'), fetch('/api/blueprints')]);
             if (!mapRes.ok || !blueprintRes.ok) throw new Error('Could not load maps and collections. Try again.');