Add administrative brand color presets (Red, Orange, Yellow) for Caresphere theme

Problem/Motivation

The site currently has a fixed brand identity centered around a single Red color scheme. To give site administrators more flexibility in managing the brand's visual impact, we need the ability to switch the primary brand colors site-wide without needing developer intervention or custom CSS updates.

Steps to reproduce

An administrator wants to change the site’s primary color from Red to Orange for a specific campaign. Currently, there is no option in the administration interface to do this, making it impossible for a non-technical user to manage the brand identity.

Proposed resolution

Introduce a "Brand Preset" feature within the theme settings. This will allow administrators to select from three professionally curated color palettes:

• Caresphere Red: The classic, high-energy brand look.
• Caresphere Orange: A warm, vibrant alternative for secondary branding.
• Caresphere Yellow: A bright, optimistic scheme optimized for readability and contrast.

Selecting a preset will automatically update buttons, highlights, icons, and specialized backgrounds across the entire site.

Remaining tasks

• Define the three brand-approved color schemes.
• Create the selection interface in the theme settings.
• Ensure all interactive elements (buttons, links, hover states) update consistently.
• Perform accessibility checks on the Yellow scheme to ensure text remains legible on bright backgrounds.

User interface changes

A simple selection menu will be added to the Theme Settings page. Administrators will see a list of brand schemes with labels, allowing them to change the site's look with a single click and save.

API changes

None.

Data model changes

The theme will now store and remember the administrator's chosen brand color preset.