chore: improve invitation flow, update project dependencies and documentation for Next.js 16 (#408)

* chore: update project dependencies and documentation for Next.js 16

- Upgraded Next.js from version 15 to 16 across various documentation files and components.
- Updated references to Next.js 16 in AGENTS.md and CLAUDE.md for consistency.
- Incremented application version to 2.21.0 in package.json.
- Refactored identity setup components to improve user experience and added confirmation dialogs for authentication methods.
- Enhanced invitation flow with new logic for handling user redirection and token generation.

* refactor: streamline invitation flow in e2e tests

- Simplified the invitation flow test by using a predefined email instead of generating a random one.
- Removed unnecessary steps such as clearing cookies and reloading the page before user sign-up.
- Enhanced clarity by eliminating commented-out code related to identity verification and user membership checks.

* refactor: improve code readability in IdentitiesPage and UpdatePasswordForm components

- Enhanced formatting of JSX elements in IdentitiesPage and UpdatePasswordForm for better readability.
- Adjusted indentation and line breaks to maintain consistent coding style across components.

* refactor: enhance LinkAccountsList component with user redirection logic

- Updated the LinkAccountsList component to include a redirectToPath option in the useLinkIdentityWithProvider hook for improved user experience.
- Removed redundant user hook declaration to streamline the code structure.

* refactor: update account setup logic in JoinTeamAccountPage

- Introduced a check for email-only authentication support to streamline account setup requirements.
- Adjusted the conditions for determining if a new account should set up additional authentication methods, enhancing user experience for new users.

packages/mcp-server/src/tools/prompts.ts

@@ -75,7 +75,7 @@ export class PromptsManager {
 - Proper error handling with try/catch and typed error objects
 - Clean, clear, well-designed code without obvious comments
 
-**React & Next.js 15 Best Practices:**
+**React & Next.js 16 Best Practices:**
 - Functional components only with 'use client' directive for client components
 - Encapsulate repeated blocks of code into reusable local components
 - Avoid useEffect (code smell) - justify if absolutely necessary