Gitea versions up to and including 1.26.1 allow OAuth2 access token scope enforcement to be bypassed through HTTP Basic authentication.

Affected: Go: code.gitea.io/gitea

### Summary

Gitea fails to enforce OAuth2 access token scopes when the token is submitted via HTTP Basic authentication instead of a Bearer token. An OAuth2 application granted only `read:user` can use the same token as `Authorization: Basic base64(<token>:x-oauth-basic)` and perform write actions, including modifying profiles, adding email addresses, creating repositories, and deleting repositories as the authorizing user.

### Details

**Root cause:** `services/auth/basic.go` accepts OAuth2 access tokens through the Basic auth path but does not store the token scope in the request context:

```go // services/auth/basic.go if uid != 0 { store.GetData()["LoginMethod"] = OAuth2TokenMethodName store.GetData()["IsApiToken"] = true // scope is NOT set return u, nil } ```

The scope enforcement middleware in `routers/api/v1/api.go` exits early when `ApiTokenScope` is absent:

```go // routers/api/v1/api.go — tokenRequiresScopes scope, scopeExists := ctx.Data["ApiTokenScope"].(auth_model.AccessTokenScope) if ctx.Data["IsApiToken"] != true || !scopeExists { return //<- exits without checking scope, all actions permitted } ```

When a token arrives via Bearer, `ApiTokenScope` is populated and scope checks apply normally. When the same token arrives via Basic auth, `ApiTokenScope` is never set, so `tokenRequiresScopes` returns immediately and no scope is enforced.

**Suggested fix:** When an OAuth2 access token is accepted in `services/auth/basic.go`, populate `A…

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