gwy: Auth0 log-ins and memory profiling

[mjcurran]

SFDS-340
Restores dual sign-in functionality (Auth0 and uname/password).
Adds a memory profiler annotation to help debug out-of-memory issues.

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Note

Low Risk
Changes are limited to login navigation, template/CSS copy, and an optional diagnostics decorator with no auth logic changes in Python.

Overview
Restores dual sign-in by routing the navbar Sign In link to account_login when SOCIALACCOUNT_ONLY is off, and to auth0_login when social-only mode is enabled (previously the nav always pointed at Auth0).

Social login UI is updated: provider buttons use Continue with {provider} copy, a shared bracket icon, and new social-provider-button / .provider-list styles for a full-width grid layout on the hero. The optional third-party section heading now says third-party ID provider.

Adds a new @profile_memory decorator in api_methods/utils/profilers.py that uses tracemalloc (with a lock for nested calls) and logs current/peak MB via loguru to help debug OOM issues.

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