fix(user): restore organizations tab on user profile (#39577)

Fixes #39572

The shared user cards template calls the User-only `IsTypeBot` method.
The profile organizations tab passed `*organization.Organization` values
to that template, so `/{username}?tab=organizations` returned a 500
error.

Organizations are now converted to Users before rendering.

tests/integration/links_test.go

@@ -172,6 +172,7 @@ func testLinksAsUser(t *testing.T) {
 		"/user2",
 		"/user2?tab=stars",
 		"/user2?tab=activity",
+		"/user2?tab=organizations",
 		"/user/settings",
 		"/user/settings/account",
 		"/user/settings/security",