fix: make /repos/search?uid=-2 return zero results, no repos with that owner (#12144)

API calls to `.../api/v1/repos/search?uid=-2&archived=false` currently do not apply the filter `uid` because of the negative value.  This can occur when APIs are interacting with `${{ forgejo.token }}` and believe they're operating as the Forgejo Actions user, which has UID -2.

In combination with the security checks that occur in the `/repos/search` API to validate that repositories accessed are visible to the user, this can result in 500 error responses when a more correct expectation would be to receive no repositories:

da8898822c/routers/api/v1/repo/repo.go (L237-L242)

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### Tests for Go changes

- I added test coverage for Go changes...
  - [ ] in their respective `*_test.go` for unit tests.
  - [x] in the `tests/integration` directory if it involves interactions with a live Forgejo server.
- I ran...
  - [x] `make pr-go` before pushing

### Documentation

- [ ] I created a pull request [to the documentation](https://codeberg.org/forgejo/docs) to explain to Forgejo users how to use this change.
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### Release notes

- [x] This change will be noticed by a Forgejo user or admin (feature, bug fix, performance, etc.). I suggest to include a release note for this change.
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Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/12144
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: Mathieu Fenniak <mathieu@fenniak.net>
Co-committed-by: Mathieu Fenniak <mathieu@fenniak.net>

models/repo/repo_list.go

@@ -361,7 +361,7 @@ func SearchRepositoryCondition(opts *SearchRepoOptions) builder.Cond {
 	}
 
 	// Restrict repositories to those the OwnerID owns or contributes to as per opts.Collaborate
-	if opts.OwnerID > 0 {
+	if opts.OwnerID != 0 {
 		accessCond := builder.NewCond()
 		if !opts.Collaborate.ValueOrZeroValue() {
 			accessCond = builder.Eq{"owner_id": opts.OwnerID}