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>

packages/db/src/schema/assets.ts

@@ -0,0 +1,26 @@
+import { pgTable, uuid, text, integer, timestamp, index, uniqueIndex } from "drizzle-orm/pg-core";
+import { companies } from "./companies.js";
+import { agents } from "./agents.js";
+
+export const assets = pgTable(
+  "assets",
+  {
+    id: uuid("id").primaryKey().defaultRandom(),
+    companyId: uuid("company_id").notNull().references(() => companies.id),
+    provider: text("provider").notNull(),
+    objectKey: text("object_key").notNull(),
+    contentType: text("content_type").notNull(),
+    byteSize: integer("byte_size").notNull(),
+    sha256: text("sha256").notNull(),
+    originalFilename: text("original_filename"),
+    createdByAgentId: uuid("created_by_agent_id").references(() => agents.id),
+    createdByUserId: text("created_by_user_id"),
+    createdAt: timestamp("created_at", { withTimezone: true }).notNull().defaultNow(),
+    updatedAt: timestamp("updated_at", { withTimezone: true }).notNull().defaultNow(),
+  },
+  (table) => ({
+    companyCreatedIdx: index("assets_company_created_idx").on(table.companyId, table.createdAt),
+    companyProviderIdx: index("assets_company_provider_idx").on(table.companyId, table.provider),
+    companyObjectKeyUq: uniqueIndex("assets_company_object_key_uq").on(table.companyId, table.objectKey),
+  }),
+);