feat(core): consolidate auth service into backend and implement stripe billing

This commit performs a major architectural refactor by migrating the standalone `auth-service` into the main `backend` application, enabling a unified codebase and simplified deployment. It also introduces comprehensive Stripe billing support and a new administrative dashboard.

Key changes:
- **Architecture**: Deleted `apps/auth-service` and integrated its functionality (JWT, magic links, OAuth, user management) into `apps/backend`.
- **Billing**: Added Stripe integration to `backend`, supporting both monthly and yearly subscription cycles with automatic plan entitlement enforcement (e.g., location limits).
- **Admin Dashboard**: Implemented a new administrative service and API endpoints to manage tenants, users, and view platform-wide statistics.
- **Frontend**:
    - Added a new pricing page with monthly/yearly toggle and comparison table.
    - Integrated Stripe and Sentry for payments and error tracking.
    - Improved dashboard UX/UI and added i18n support for new features.
    - Enhanced the public booking flow with better validation and contact form integration.
- **Database**: Added migrations for users, magic links, password resets, OAuth states, admin audit logs, and refresh tokens.
- **DevOps**: Updated environment configurations for Railway and Vercel, and streamlined the project's `package.json` scripts.

prompt.md

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-Continue enhancing the bookra dashboard - fix better style add move things, make it fully working, dark white mode, make it really nice add pages test all. Feature and function wise, we here manage bookings only. The payments are  not related to the business using our service but business subscription to our saas so something like this Payment
+http://localhost:3000/dashboard looks preatty shit, multi color messed up not tied to the brand styling, fix it, make it better use fully @design-taste-frontend  @frontend-design  make it appealing, in the current stage i would not want to use it, style it to the app take inspiration from the landing page. all the pages in the left nav in dashboard don't do anything, looks weird, feels weird, does not work. we need to heavily work on this, take your time @brainstorming  @tdvorak-fullstack  use all these skills, fix it. also remove footer from the dashboard. dont stop untill finished and proud of what you did.
 
-$120 received
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-15 min ago should not be there. make it  really easy and  fully working for the admin to see all the booking manage them, add zones and days the user cannot register add make it really nice. Also can you add an open endpoint for each businness, endpoint they can use which would have the dashboard for registration for their customers. Lets say they share a link to bookra.eu/sportcreative the customers see calendar or other types of view where they can book some date. Login/register, when booking we need their mail and so on.
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-The  main workflow should be - business goes to bookra.eu they see the landing page about what we offer, demo mode, all info about us. If they like it they can go and register their business, choose pricing plan and setup their business, place, sector, brading,... They get access to their specific dashborad where they can manage all the bookings. They should first be shown a modal to implement bookra to their page either our hosted page at their endpoint like i told you previously, or widget to integrate  to e.x. html+js, react, ts, solidjs, php/wordpress or basically anywhere they like. We in this widget  add some specifier which manages auth, that the registration goes  to the specific business, fully routed,  secure and working. Now for the business customers. They go to the link or interact with the widget - they pick a date in the calendar or dropdown or whatever, they add their name, mail, pick location if the business has multiple locations (also based on the businesses pricing plan they picked). After they register we send them confirmation mail and also in the mail management link - which if they click on can change the registration, change location do whatever, see more info nice and stylized page where they can see all info. Also we send this to the business dashboard and their mail that they got a new registration and restrict the space in the calendar so no double booking, here the business can also manage the customer, we autolink with previous customers, filter to the customers show all their previous and next booking. They can change e.x. the booking date and time if this change happens we again send info to the businesses customer that their booking has changed and again attach the management page where they can even contact the business like a chat page so they can talk about the change, and more communicate with each other. So it should be fully  wired like this. Also when the day gets closer e.x. the day after and the exact day we send reminder to the businesses customer that their registration  is tommorrow/today at this time and this location. Make all these really nicely styled to our style or the businesses custom style if they choose - they can edit the mails, colors, also we attach the business branding in the mail by default, make it fully work and nice like this.
+fix calendar style better, on day calendar click show modal in which is the reservation or the entry. also show on click on the reservation more info. add cs en translation button, make sure everything translated. the top dashboard graph not visible not working. notification not working not implemented. fix the demo mode make it better take your time analyse first also use @caveman