feat(reins): upload file and archive sources to knowledge

[mykyta-torbynskyi]

What

Enables file and archive (.zip) uploads as knowledge sources. Previously only text and URL sources worked; file and archive uploads silently failed.

Why

File/archive uploads went through a raw $fetch to a relative /api path with no auth, while text/url sources used the configured axios client (baseURL + Bearer interceptor). The backend also had no working S3 upload path for streamed archive entries.

Changes

• admin: route multipart uploads through apiClient.instance so they reach the API origin with auth; add an archive upload form and the matching store action.
• api: buffer the multipart upload to a temp file for extraction; implement uploadFileStream as a buffered S3 PutObject; run the archive import in the background (one file-source per entry) and return the detected count immediately.
• api: new archive.extractor (lazy per-entry zip streaming, skips unsupported files and macOS metadata) plus AddFromArchiveResultDto.
• terraform: provision the reins_sources S3 bucket and retire pg_backups via removed blocks (drops them from state without deleting the AWS bucket).

Verification

• nest build passes clean (exit 0), dist emitted.
• admin typecheck clean for the changed store and components.
• Not yet runtime-tested in the browser.