feat(org): add team visibility so org members can discover teams (#37680)

Closes #37670.

Today, org members in Gitea only see teams they're a member of. In
larger orgs that hurts onboarding and discoverability — there's no way
to look up which team owns what without asking around. GitHub solves
this with a per-team visibility setting; this PR brings the same model
to Gitea.

## What changes

- Every team gets a `visibility` setting:
- `private` *(default)* — only team members and org owners can see the
team. Same as today's behavior.
- `limited` — listable by any member of the organization. Members and
the repos the team has access to are visible too. Non-org-members still
see nothing.
  - `public` — listable by any signed-in user.
- The Owners team visibility is fixed and cannot be changed via
settings.
- Existing teams default to `private`, so this is a no-op for anyone who
doesn't change anything.

## API

- `Team`, `CreateTeamOption`, `EditTeamOption` all gain a `visibility`
field (string enum: `private` | `limited` | `public`).
- `GET /orgs/{org}/teams` and `/orgs/{org}/teams/search` now apply the
same visibility rules as the web UI:
  - site admins and org owners still see every team
- other org members see their own teams plus any `limited` or `public`
team
  - `private` teams are no longer leaked through these endpoints
- Swagger/OpenAPI specs regenerated.

## UI

View from admin2 (not an owner):
<img width="1669" height="726"
src="https://github.com/user-attachments/assets/daf4bccb-644b-4426-b178-71963aeaf73b"
/>

View from admin (owner):

<img width="2559" height="863"
src="https://github.com/user-attachments/assets/4f22cebc-e9df-4fd2-8ed4-724d31fadb7a"
/>

---------

Signed-off-by: bircni <bircni@icloud.com>
Co-authored-by: TheFox0x7 <thefox0x7@gmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/api/v1/org/team.go

@@ -55,10 +55,15 @@ func ListTeams(ctx *context.APIContext) {
 	//     "$ref": "#/responses/notFound"
 
 	listOptions := utils.GetListOptions(ctx)
-	teams, count, err := organization.SearchTeam(ctx, &organization.SearchTeamOptions{
+	opts := &organization.SearchTeamOptions{
 		ListOptions: listOptions,
 		OrgID:       ctx.Org.Organization.ID,
-	})
+	}
+	if err := organization.ApplyTeamListFilter(ctx, ctx.Org.Organization.ID, ctx.Doer, ctx.IsSigned, opts); err != nil {
+		ctx.APIErrorInternal(err)
+		return
+	}
+	teams, count, err := organization.SearchTeam(ctx, opts)
 	if err != nil {
 		ctx.APIErrorInternal(err)
 		return
@@ -218,6 +223,7 @@ func CreateTeam(ctx *context.APIContext) {
 		IncludesAllRepositories: form.IncludesAllRepositories,
 		CanCreateOrgRepo:        form.CanCreateOrgRepo,
 		AccessMode:              teamPermission,
+		Visibility:              organization.NormalizeTeamVisibility(string(form.Visibility)),
 	}
 
 	if team.AccessMode < perm.AccessModeAdmin {
@@ -295,6 +301,10 @@ func EditTeam(ctx *context.APIContext) {
 		team.Description = *form.Description
 	}
 
+	if form.Visibility != nil && !team.IsOwnerTeam() {
+		team.Visibility = organization.NormalizeTeamVisibility(string(*form.Visibility))
+	}
+
 	isAuthChanged := false
 	isIncludeAllChanged := false
 	if !team.IsOwnerTeam() && len(form.Permission) != 0 {
@@ -387,15 +397,6 @@ func GetTeamMembers(ctx *context.APIContext) {
 	//   "404":
 	//     "$ref": "#/responses/notFound"
 
-	isMember, err := organization.IsOrganizationMember(ctx, ctx.Org.Team.OrgID, ctx.Doer.ID)
-	if err != nil {
-		ctx.APIErrorInternal(err)
-		return
-	} else if !isMember && !ctx.Doer.IsAdmin {
-		ctx.APIErrorNotFound()
-		return
-	}
-
 	listOptions := utils.GetListOptions(ctx)
 	teamMembers, err := organization.GetTeamMembers(ctx, &organization.SearchMembersOptions{
 		ListOptions: listOptions,
@@ -574,14 +575,20 @@ func GetTeamRepos(ctx *context.APIContext) {
 		ctx.APIErrorInternal(err)
 		return
 	}
-	repos := make([]*api.Repository, len(teamRepos))
-	for i, repo := range teamRepos {
+	repos := make([]*api.Repository, 0, len(teamRepos))
+	for _, repo := range teamRepos {
 		permission, err := access_model.GetDoerRepoPermission(ctx, repo, ctx.Doer)
 		if err != nil {
 			ctx.APIErrorInternal(err)
 			return
 		}
-		repos[i] = convert.ToRepo(ctx, repo, permission)
+		// A team's repo list is reachable by non-team-members through the team's
+		// visibility tier, so never expose repos (incl. their names) the doer
+		// cannot access.
+		if !permission.HasAnyUnitAccessOrPublicAccess() {
+			continue
+		}
+		repos = append(repos, convert.ToRepo(ctx, repo, permission))
 	}
 	ctx.SetLinkHeader(int64(team.NumRepos), listOptions.PageSize)
 	ctx.SetTotalCountHeader(int64(team.NumRepos))
@@ -633,6 +640,12 @@ func GetTeamRepo(ctx *context.APIContext) {
 		ctx.APIErrorInternal(err)
 		return
 	}
+	// The team may be reachable by a non-team-member via its visibility tier;
+	// don't confirm the existence of a repo the doer cannot access.
+	if !permission.HasAnyUnitAccessOrPublicAccess() {
+		ctx.APIErrorNotFound()
+		return
+	}
 
 	ctx.JSON(http.StatusOK, convert.ToRepo(ctx, repo, permission))
 }
@@ -806,9 +819,9 @@ func SearchTeam(ctx *context.APIContext) {
 		ListOptions: listOptions,
 	}
 
-	// Only admin is allowed to search for all teams
-	if !ctx.Doer.IsAdmin {
-		opts.UserID = ctx.Doer.ID
+	if err := organization.ApplyTeamListFilter(ctx, ctx.Org.Organization.ID, ctx.Doer, ctx.IsSigned, opts); err != nil {
+		ctx.APIErrorInternal(err)
+		return
 	}
 
 	teams, maxResults, err := organization.SearchTeam(ctx, opts)