fix(login): integration tests failing due to React 19 SSR errors (#10613)

# Which Problems Are Solved

Integration tests were failing with Minified React error 419 caused by
React 19 Suspense boundary issues during server-side rendering (SSR) to
client-side rendering (CSR) transitions.

# How the Problems Are Solved

The fix handles infrastructure-level SSR errors gracefully while
maintaining proper error detection for actual application issues.

- Added Cypress error handling for React 19 SSR hydration errors that
don't affect functionality

# Additional Changes

Enhanced Next.js configuration with React 19 compatibility
optimizations:
- `optimizePackageImports`: @radix-ui/react-tooltip and @heroicons/react
can have large bundle sizes if not optimized. Such packages are
suggested to be optimized in
https://nextjs.org/docs/app/api-reference/config/next-config-js/optimizePackageImports
- `poweredByHeader`: Not that important. Benefits are smaller HTTP
headers, Tiny bandwidth savings, and more professional appearance due to
cleaner response headers, added it as a "security best practice".


# Additional Context

- Replaces #10611

apps/login/integration/integration/invite.cy.ts

@@ -89,7 +89,7 @@ describe("verify invite", () => {
     });
   });
 
-  it.only("shows authenticators after successful invite verification", () => {
+  it("shows authenticators after successful invite verification", () => {
     stub("zitadel.user.v2.UserService", "VerifyInviteCode");
 
     cy.visit("/verify?userId=221394658884845598&code=abc&invite=true");