AuthGate redirected anonymous users to /cp/auth/login?return_to=<url>,
but the login page itself triggered AuthGate, which redirected again
with double-encoded return_to. Each redirect added another encoding
layer until the URL exceeded 431 (Request Header Fields Too Large).
Two guards:
1. redirectToLogin() returns early if already on /cp/auth/* path
2. AuthGate skips redirect check entirely for /cp/auth/* paths
[Molecule-Platform-Evolvement-Manager]
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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