feat: Presigned object URLs (s3 driver)

POST /buckets/:id/object-presigns mints SigV4 query-signed GET/PUT
URLs so clients move bytes directly against S3 — large transfers skip
the backend entirely.

- storage.Presigner optional interface; S3Store implements, local
  driver returns a clear error (no external surface to sign).
- TTL 60s–1h (default 15m); download requires read role + existing
  object row (no key probing); upload requires write role.
- S3_PUBLIC_ENDPOINT rewrites the client-facing host for internal
  S3_ENDPOINTs — signatures bind the host, URLs are valid only where
  minted.
- CLI: primora objects:presign <bucket> <key> [--upload] [--ttl].

Verified live against cloudserver: GET fetched the object with no
auth headers; PUT pushed 1 MB direct to S3; unsigned list → 403;
untracked-key download presign → 404.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

packages/api-client/src/generated/index.ts

@@ -108,6 +108,8 @@ export type { OrganizationSummary } from './models/OrganizationSummary';
 export type { PaginationLimit } from './models/PaginationLimit';
 export type { PaginationMetadata } from './models/PaginationMetadata';
 export type { PaginationOffset } from './models/PaginationOffset';
+export { PresignedURL } from './models/PresignedURL';
+export { PresignObjectRequest } from './models/PresignObjectRequest';
 export type { Project } from './models/Project';
 export type { ProjectID } from './models/ProjectID';
 export { ProjectMember } from './models/ProjectMember';
@@ -258,6 +260,8 @@ export { $OrganizationSummary } from './schemas/$OrganizationSummary';
 export { $PaginationLimit } from './schemas/$PaginationLimit';
 export { $PaginationMetadata } from './schemas/$PaginationMetadata';
 export { $PaginationOffset } from './schemas/$PaginationOffset';
+export { $PresignedURL } from './schemas/$PresignedURL';
+export { $PresignObjectRequest } from './schemas/$PresignObjectRequest';
 export { $Project } from './schemas/$Project';
 export { $ProjectID } from './schemas/$ProjectID';
 export { $ProjectMember } from './schemas/$ProjectMember';