Add configurable multi-provider SSO, SSO-only mode, and JIT controls via auth.yml (#441)

* Add configuration and logic for dynamic SSO provider support and stricter JIT account creation

- Introduced `config/auth.yml` for centralized auth configuration and documentation.
- Added support for multiple SSO providers, including Google, GitHub, and OpenID Connect.
- Implemented stricter JIT SSO account creation modes (`create_and_link` vs `link_only`).
- Enabled optional restriction of JIT creation by allowed email domains.
- Enhanced OmniAuth initializer for dynamic provider setup and better configurability.
- Refined login UI to handle local login disabling and emergency super-admin override.
- Updated account creation flow to respect JIT mode and domain checks.
- Added tests for SSO account creation, login form visibility, and emergency overrides.

# Conflicts:
#	app/controllers/sessions_controller.rb

* remove non-translation

* Refactor authentication views to use translation keys and update locale files

- Extracted hardcoded strings in `oidc_accounts/link.html.erb` and `sessions/new.html.erb` into translation keys for better localization support.
- Added missing translations for English and Spanish in `sessions` and `oidc_accounts` locale files.

* Enhance OmniAuth provider configuration and refine local login override logic

- Updated OmniAuth initializer to support dynamic provider configuration with `name` and scoped parameters for Google and GitHub.
- Improved local login logic to enforce stricter handling of super-admin override when local login is disabled.
- Added test for invalid super-admin override credentials.

* Document Google sign-in configuration for local development and self-hosted environments

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Co-authored-by: Josh Waldrep <joshua.waldrep5+github@gmail.com>

Gemfile

@@ -77,10 +77,12 @@ gem "rqrcode", "~> 3.0"
 gem "activerecord-import"
 gem "rubyzip", "~> 2.3"
 
-# OpenID Connect authentication
+# OpenID Connect & OAuth authentication
 gem "omniauth", "~> 2.1"
 gem "omniauth-rails_csrf_protection"
 gem "omniauth_openid_connect"
+gem "omniauth-google-oauth2"
+gem "omniauth-github"
 
 # State machines
 gem "aasm"