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>

server/src/services/index.ts

@@ -13,3 +13,4 @@ export { dashboardService } from "./dashboard.js";
 export { sidebarBadgeService } from "./sidebar-badges.js";
 export { logActivity, type LogActivityInput } from "./activity-log.js";
 export { publishLiveEvent, subscribeCompanyLiveEvents } from "./live-events.js";
+export { createStorageServiceFromConfig, getStorageService } from "../storage/index.js";