enhance: inherit team access for all units (#38938)

Admin and write team authorize now grant that mode on every unit,
including units added later, instead of only rows present in
`team_unit`. Granular teams keep `authorize=none` and explicit unit
rows.

Closes the `TEAM-UNIT-PERMISSION` design gap from
https://github.com/go-gitea/gitea/pull/34128.

Maybe also fix #15962 (actually maybe it had been fixed before, the root
cause is out-of-sync "access" table)


## Screenshots

only writing selected:
<img width="1399" height="1007" alt="image"
src="https://github.com/user-attachments/assets/1d1b4c49-a59a-47b6-998f-0464a067395b"
/>


_Created with the help of AI_

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

tests/integration/api_issue_templates_test.go

@@ -57,7 +57,7 @@ func TestAPIIssueTemplateRequiresCodeUnit(t *testing.T) {
 
 	repo := unittest.AssertExistsAndLoadBean(t, &repo_model.Repository{ID: 24})
 	user := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 2})
-	token := getUserToken(t, user.Name, auth_model.AccessTokenScopeReadRepository)
+	token := getUserToken(t, user.Name, auth_model.AccessTokenScopeReadUser)
 	issueTemplatesURL := "/api/v1/repos/" + repo.FullName() + "/issue_templates"
 	languagesURL := "/api/v1/repos/" + repo.FullName() + "/languages"