Table stored_files {
  id bigserial [pk]
  guid uuid [unique, not null, default: `gen_random_uuid()`]
  thought_id uuid [ref: > thoughts.guid]
  project_id uuid [ref: > projects.guid]
  name text [not null]
  media_type text [not null]
  kind text [not null, default: 'file']
  encoding text [not null, default: 'base64']
  size_bytes bigint [not null]
  sha256 text [not null]
  content bytea [not null]
  created_at timestamptz [not null, default: `now()`]
  updated_at timestamptz [not null, default: `now()`]

  indexes {
    thought_id
    project_id
    sha256
  }
}

// Cross-file refs (for relspecgo merge)
Ref: stored_files.thought_id > thoughts.guid [delete: set null]
Ref: stored_files.project_id > projects.guid [delete: set null]