LinkSharing.CanRead resolved the parent project from the share hash, but a
by-id read (GET /projects/{project}/shares/{share}) only carries the numeric
id, never the hash — so the project lookup returned ErrProjectShareDoesNotExist
and every read-one 404'd, even for the share's owner. This affected both v1 and
v2.
Resolve the project from ProjectID when it is set (the by-id read path), keeping
the hash lookup as a fallback for resolving a share purely by its public hash.
The permission semantic is unchanged — you can read a share if you can read its
parent project; only the project lookup changes. ReadOne still scopes by
id AND project_id, so a share id from another project the caller can access is
not leaked (404, no IDOR).
Flips the v2 webtest's pinned 404 cases to assert success and adds the
cross-project IDOR and non-member negatives.
kolaente