* Upgraded to Next.js 16
* Refactored code to comply with React 19.2 ESLint rules
* Refactored some useEffect usages with the new useEffectEvent
* Added Identities page and added second step to set up an identity after accepting an invitation
* Updated all dependencies
* Introduced PNPM catalogs for some frequently updated dependencies
* Bugs fixing and improvements
Replaced specific object paths with generic type helpers across several files to enhance readability and maintainability. This change standardizes the import patterns and type definitions for database tables and enums.
Changed the billing provider in the `.env.development` file from Stripe to Lemon Squeezy. This requires adaptations at many levels: at the web app to load Lemon Squeezy's script in the checkout process, at the billing gateway to handle Lemon Squeezy calls, and in the database to reflect the current billing provider. The checkout process is now done using Lemon Squeezy Sessions and its billing strategy was adjusted accordingly. Billing-related components and services were also updated.
