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/src/factory.spec.ts

@@ -0,0 +1,132 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+
+// Mock the client module — StorageClient must be a class
+vi.mock('./client', () => ({
+	StorageClient: vi.fn(function (this: Record<string, unknown>) {
+		this.upload = vi.fn();
+		this.getBucketName = vi.fn();
+	}),
+}));
+
+import {
+	createStorage,
+	createStorageClient,
+	createPictureStorage,
+	createChatStorage,
+} from './factory';
+import { BUCKETS } from './types';
+import { StorageClient } from './client';
+
+describe('createStorage', () => {
+	beforeEach(() => {
+		process.env.NODE_ENV = 'development';
+	});
+
+	afterEach(() => {
+		delete process.env.PICTURE_STORAGE_PUBLIC_URL;
+		delete process.env.PICTURE_CDN_URL;
+	});
+
+	it('creates a client with the correct bucket name', () => {
+		createStorage('PICTURE');
+
+		expect(StorageClient).toHaveBeenCalledWith(
+			expect.any(Object),
+			expect.objectContaining({ name: BUCKETS.PICTURE })
+		);
+	});
+
+	it('resolves public URL from environment', () => {
+		process.env.PICTURE_STORAGE_PUBLIC_URL = 'https://cdn.example.com/picture';
+
+		createStorage('PICTURE');
+
+		expect(StorageClient).toHaveBeenCalledWith(
+			expect.any(Object),
+			expect.objectContaining({ publicUrl: 'https://cdn.example.com/picture' })
+		);
+	});
+
+	it('resolves CDN URL from environment', () => {
+		process.env.PICTURE_CDN_URL = 'https://cdn.fast.com/picture';
+
+		createStorage('PICTURE');
+
+		expect(StorageClient).toHaveBeenCalledWith(
+			expect.any(Object),
+			expect.objectContaining({ cdnUrl: 'https://cdn.fast.com/picture' })
+		);
+	});
+
+	it('allows explicit publicUrl override', () => {
+		process.env.PICTURE_STORAGE_PUBLIC_URL = 'https://from-env.com';
+
+		createStorage('PICTURE', 'https://explicit.com');
+
+		expect(StorageClient).toHaveBeenCalledWith(
+			expect.any(Object),
+			expect.objectContaining({ publicUrl: 'https://explicit.com' })
+		);
+	});
+});
+
+describe('convenience aliases', () => {
+	it('createPictureStorage creates PICTURE bucket', () => {
+		createPictureStorage();
+
+		expect(StorageClient).toHaveBeenCalledWith(
+			expect.any(Object),
+			expect.objectContaining({ name: BUCKETS.PICTURE })
+		);
+	});
+
+	it('createChatStorage creates CHAT bucket', () => {
+		createChatStorage();
+
+		expect(StorageClient).toHaveBeenCalledWith(
+			expect.any(Object),
+			expect.objectContaining({ name: BUCKETS.CHAT })
+		);
+	});
+});
+
+describe('createStorageClient', () => {
+	afterEach(() => {
+		process.env.NODE_ENV = 'development';
+		delete process.env.S3_ENDPOINT;
+		delete process.env.S3_ACCESS_KEY;
+		delete process.env.S3_SECRET_KEY;
+	});
+
+	it('throws when endpoint is missing in production', () => {
+		process.env.NODE_ENV = 'production';
+		process.env.S3_ENDPOINT = '';
+
+		expect(() => createStorageClient(BUCKETS.CHAT)).toThrow('S3_ENDPOINT is required');
+	});
+
+	it('throws when credentials are missing in production', () => {
+		process.env.NODE_ENV = 'production';
+		process.env.S3_ENDPOINT = 'https://s3.example.com';
+		process.env.S3_ACCESS_KEY = '';
+		process.env.S3_SECRET_KEY = '';
+
+		expect(() => createStorageClient(BUCKETS.CHAT)).toThrow(
+			'S3_ACCESS_KEY and S3_SECRET_KEY are required'
+		);
+	});
+
+	it('uses MinIO defaults in development', () => {
+		process.env.NODE_ENV = 'development';
+
+		createStorageClient(BUCKETS.CHAT);
+
+		expect(StorageClient).toHaveBeenCalledWith(
+			expect.objectContaining({
+				endpoint: 'http://localhost:9000',
+				accessKeyId: 'minioadmin',
+			}),
+			expect.any(Object)
+		);
+	});
+});