NethVoice: Add rebranding configuration interface

[tonyco97]

Description

NethVoice now supports complete customization of the brand identity for the installation, allowing administrators to adapt the interface to their corporate style.

Proposed solution

Implement a dedicated administration page (Rebranding) that allows configuring:

1. NethVoice CTI — Customize CTI login with:

   • Product name (replaces "NethVoice")
   • Logo for light and dark theme
   • Square logo for navbar
   • Favicon
   • Login background image
   • Login illustration toggle

2. NethVoice Admin (Wizard) — Customize configuration wizard with:

   • Product name
   • Logo
   • Favicon
   • Background image

3. PBX Report — Customize Reports login with:

   • Product name
   • Logo
   • Favicon
   • Background image

The administration page uses Carbon tabs (like in Backup and Restore) to logically organize the three sections, maintaining a single submit to save all configurations. Each section includes a live preview of the customized login.

Additional context

• All branding values are stored in the database and synchronized in the NS8 module
• Images must be public URLs in SVG format

See also

• Branch PR: nethesis/ns8-nethvoice/rebranding
• Related commits on nethvoice-report