Fix S3 provider to use async generator for web stream conversion instead
of Readable.fromWeb, add postForm helper and attachment API methods to
the UI client, and add local disk storage provider tests.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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>
