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>

build/openapi3gen/enumscan.go

@@ -34,13 +34,16 @@ func EnumKey(values []any) string {
 var rxSwaggerEnum = regexp.MustCompile(`swagger:enum\s+(\w+)`)
 
 // ScanSwaggerEnumTypes walks .go files under each dir and returns a map from
-// a canonical value-set key (see EnumKey) to the Go type name declared with
-// // swagger:enum TypeName.
+// a canonical value-set key (see EnumKey) to the Go type names declared with
+// // swagger:enum TypeName. Multiple type names per key are allowed (e.g.
+// distinct enum types that happen to share a value set such as
+// {public, limited, private}); callers must disambiguate per-usage (typically
+// by parsing the property's x-go-enum-desc extension to recover the const
+// type prefix).
 //
-// Returns an error on parse failure, on an annotation for a type whose
-// constants can't be extracted, or on value-set collisions between two
-// different enum types.
-func ScanSwaggerEnumTypes(dirs []string) (map[string]string, error) {
+// Returns an error on parse failure or on an annotation for a type whose
+// constants can't be extracted.
+func ScanSwaggerEnumTypes(dirs []string) (map[string][]string, error) {
 	fset := token.NewFileSet()
 	parsed := []*ast.File{}
 
@@ -92,17 +95,18 @@ func ScanSwaggerEnumTypes(dirs []string) (map[string]string, error) {
 		}
 	}
 
-	result := map[string]string{}
+	result := map[string][]string{}
 	for typeName := range enumTypes {
 		values, ok := enumValues[typeName]
 		if !ok || len(values) == 0 {
 			return nil, fmt.Errorf("swagger:enum %s has no const block with typed string values", typeName)
 		}
 		key := EnumKey(values)
-		if existing, ok := result[key]; ok && existing != typeName {
-			return nil, fmt.Errorf("swagger:enum value-set collision: %s and %s both use %q", existing, typeName, key)
-		}
-		result[key] = typeName
+		result[key] = append(result[key], typeName)
+	}
+	for key, names := range result {
+		sort.Strings(names)
+		result[key] = names
 	}
 	return result, nil
 }