Add platform-dash: S3 artifact browser for Garage object store

Lightweight Next.js app for browsing, uploading, and downloading
artifacts from the cluster-local Garage S3 bucket. Uses the harness
design system. Features:
- File/folder browser with breadcrumb navigation
- Drag-and-drop upload
- Download and delete
- Ingress at platform.coreworlds.io (internal-only)

Also adds platform-dash to CI/deploy workflows.

apps/platform-dash/package.json

@@ -0,0 +1,25 @@
+{
+  "name": "@homelab/platform-dash",
+  "version": "0.1.0",
+  "private": true,
+  "scripts": {
+    "dev": "next dev -p 3200",
+    "build": "next build",
+    "start": "next start -p 3200",
+    "lint": "next lint",
+    "test": "echo 'no tests yet'"
+  },
+  "dependencies": {
+    "@aws-sdk/client-s3": "^3.750.0",
+    "@aws-sdk/s3-request-presigner": "^3.750.0",
+    "next": "^15.1.0",
+    "react": "^19.0.0",
+    "react-dom": "^19.0.0"
+  },
+  "devDependencies": {
+    "@types/node": "^22",
+    "@types/react": "^19",
+    "@types/react-dom": "^19",
+    "typescript": "^5.7.0"
+  }
+}