feat(ui): avatar crop modal, health endpoint, leaner Dockerfile

- Add AvatarCropModal.svelte using cropperjs v1: 1:1 crop, 400×400 output,
  JPEG/WebP output, dark glassmorphic UI
- Rewrite profile page avatar upload to use presigned PUT flow (POST→PUT→PATCH)
  instead of sending raw FormData directly; crop modal opens on file select
- Add GET /health → {status:ok} for Docker healthcheck
- Simplify Dockerfile: drop runtime npm ci (adapter-node bundles all deps)
- Fix docker-compose UI healthcheck: /health route, 127.0.0.1 to avoid
  IPv6 localhost resolution failure in alpine busybox wget

ui/package.json

@@ -27,6 +27,7 @@
 	"dependencies": {
 		"@aws-sdk/client-s3": "^3.1005.0",
 		"@aws-sdk/s3-request-presigner": "^3.1005.0",
+		"cropperjs": "^1.6.2",
 		"marked": "^17.0.3",
 		"pocketbase": "^0.26.8"
 	}