chore(login): migrate nextjs login to monorepo (#10134)

# Which Problems Are Solved

We move the login code to the zitadel repo.

# How the Problems Are Solved

The login repo is added to ./login as a git subtree pulled from the
dockerize-ci branch.
Apart from the login code, this PR contains the changes from #10116

# Additional Context

- Closes https://github.com/zitadel/typescript/issues/474
- Also merges #10116  
- Merging is blocked by failing check because of:
- https://github.com/zitadel/zitadel/pull/10134#issuecomment-3012086106

---------

Co-authored-by: Max Peintner <peintnerm@gmail.com>
Co-authored-by: Max Peintner <max@caos.ch>
Co-authored-by: Florian Forster <florian@zitadel.com>

internal/integration/config/zitadel.yaml

@@ -101,3 +101,10 @@ SystemDefaults:
   KeyConfig:
     PrivateKeyLifetime: 7200h
     PublicKeyLifetime: 14400h
+
+OIDC:
+  DefaultLoginURLV2: "/login?authRequest=" # ZITADEL_OIDC_DEFAULTLOGINURLV2
+  DefaultLogoutURLV2: "/logout?post_logout_redirect=" # ZITADEL_OIDC_DEFAULTLOGOUTURLV2
+
+SAML:
+  DefaultLoginURLV2: "/login?authRequest=" # ZITADEL_SAML_DEFAULTLOGINURLV2