First draft for filtering logic of Global book filter

[BearSunny]

Phase 1 of #10760

Technical:

This PR introduces the foundational logic for our global Book Preferences filter, which will live on the top IA bar. While the full feature is not yet implemented, the code in this phase is intended to do the following:

1. Retrieve user preferences from three sources: user account settings, session, and cookie.
2. Validate and normalize those inputs for consistent filtering.
3. Apply a layered filtering strategy: Base Config < Carousel-specific filter < User Preferences. This means user preferences will take precedence over both the base configuration and carousel-specific filter.

This logic allows users to set global preferences that automatically apply across all carousels, while still preserving each carousel's specific contents.

Testing:

This PR sets up the structure for the preference engine, but does not yet include unit tests. To proceed further, I would appreciate clarification on the following areas:

1. What are the actual Solr schema field names and default carousel configs?
2. What is the exact structure of our request object, and should we proceed under the assumption that user authentication is required?
3. Where and how should we store user preferences (e.g., in a database, in session, etc.)?
4. Which configuration file or source defines each carousel?
5. I haven't seen the implementation for Add Dropdown Menu to Facet Carousels #10512 yet, so my carousel-specific filter overrides should only be a placeholder for now.

Looking forward to your inputs on these aspects and would be happy to build on this feature in the subsequent phases!

Stakeholders:

@mekarpeles
@cdrini

[BearSunny]

Hi @mekarpeles and @cdrini,

I’ve made updates to Carousel.js, preferences.js, preferences-handler.js, alert.html, and account.py to implement a global book filter with the following flow:

1. The user submits a form via the UI.

2. JavaScript sends the preferences to the server.

3. The server processes the request, sets cookies for future use, and returns a success response.

4. Upon receiving confirmation, JavaScript triggers an event instructing the carousels to reload content using the updated preferences.

5. On subsequent page loads, preferences-handler.js hydrates localStorage with any existing filter cookies, ensuring the carousels (via Carousel.js) initialize with the correct preferences and apply them immediately on their first content fetch.

At this stage, the feature does not yet guarantee that preferences persist after a user performs a search. Oh and by the way, I'm a bit confused why there are so many changed files in this PR?