feat(storage): improve shared-storage robustness, scalability, and DX

- Fix exists() to only catch 404/NotFound, rethrow real errors
- Add downloadStream() for memory-efficient large file downloads
- Add uploadMultipart() using @aws-sdk/lib-storage for large files
- Add automatic pagination to list() via continuation tokens
- Add CDN URL support (cdnUrl in BucketConfig, getCdnUrl() method)
- Reduce factory boilerplate with generic createStorage() function
- Add MinIO lifecycle rules for tmp/ prefixes (chat 90d, calendar 30d, picture 7d)
- Add vitest setup with 56 tests covering client, factory, and utils

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/shared-storage/package.json

@@ -17,15 +17,19 @@
 	"scripts": {
 		"build": "tsc",
 		"type-check": "tsc --noEmit",
+		"test": "vitest run",
+		"test:watch": "vitest",
 		"clean": "rm -rf dist",
 		"lint": "eslint ."
 	},
 	"dependencies": {
 		"@aws-sdk/client-s3": "^3.700.0",
+		"@aws-sdk/lib-storage": "^3.700.0",
 		"@aws-sdk/s3-request-presigner": "^3.700.0"
 	},
 	"devDependencies": {
 		"@types/node": "^24.10.1",
-		"typescript": "^5.9.3"
+		"typescript": "^5.9.3",
+		"vitest": "^4.1.0"
 	}
 }