fix: Various security fixes (#38103) (#38151)

Backport #38103

- Enforce org visibility on organization label read endpoints (private
org labels no longer leak to non-members).
- Block fork sync (`merge-upstream`) when the base repo is no longer
readable (stops pulling commits after a parent goes private).
- Remove `REVERSE_PROXY_LIMIT` / `REVERSE_PROXY_TRUSTED_PROXIES` from
the Docker `app.ini` templates (the `= *` default allowed
`X-WEBAUTH-USER` impersonation; reverse-proxy auth is now opt-in and
admin-configured).
- Enforce single-use TOTP passcodes across web login, password-reset,
and Basic-Auth `X-Gitea-OTP` (fixes a TOCTOU race and a stateless
replay).
- Re-check branch write permission for every ref in a push (the
pre-receive hook cached the first ref's result, letting a per-branch
maintainer-edit grant escalate to full repo write).

---------

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

tests/integration/api_twofa_test.go

@@ -51,6 +51,12 @@ func TestAPITwoFactor(t *testing.T) {
 		AddBasicAuth(user.Name)
 	req.Header.Set("X-Gitea-OTP", passcode)
 	MakeRequest(t, req, http.StatusOK)
+
+	// the same passcode must not be replayable on the basic-auth surface (RFC 6238 single-use)
+	req = NewRequest(t, "GET", "/api/v1/user").
+		AddBasicAuth(user.Name)
+	req.Header.Set("X-Gitea-OTP", passcode)
+	MakeRequest(t, req, http.StatusUnauthorized)
 }
 
 func TestBasicAuthWithWebAuthn(t *testing.T) {