Blaze: add support for Custom Post Types

### What

Currently, Blaze only allows customers to create campaigns for standard WordPress post styles, Post and Pages, but customers should be able to advertise any content from their site, including Products, Portfolio Projects, Testimonials and CPTs created by plugins or similar

### Why

This will give customers more flexibility and make Blaze a more compelling advertising platform

### How

We should keep the Post/Page tabs and include tags for Products, and a tab that groups all other CPTs.

Start at the Blaze campaign creation flow and inspect how the existing Post and Page tabs select content. Trace how Products and other custom post types are exposed by WordPress, then define the grouping and tab behavior for Products and all remaining CPTs. Done means campaigns can advertise each requested content category while preserving the existing Post and Page tabs.

Written by the indexing model from the issue text.