feat: add storage system with local disk and S3 providers

Introduces a provider-agnostic storage subsystem for file attachments.
Includes local disk and S3 backends, asset/attachment DB schemas, issue
attachment CRUD routes with multer upload, CLI configure/doctor/env
integration, and enriched issue ancestors with project/goal resolution.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

cli/src/checks/index.ts

@@ -14,3 +14,4 @@ export { llmCheck } from "./llm-check.js";
 export { logCheck } from "./log-check.js";
 export { portCheck } from "./port-check.js";
 export { secretsCheck } from "./secrets-check.js";
+export { storageCheck } from "./storage-check.js";