Improve breadcrumb navigation: remove non-navigable items, apply Section: Item format, and audit all screens

Description

The admin breadcrumb component currently includes noise that makes navigation less clear: the "Home" item and non-navigable intermediate items (section titles without routes) appear as standalone chips, cluttering the breadcrumb trail.

Additionally, breadcrumbs are not always showing the full user path — this was confirmed in the new Edit Content screen, and likely exists in other admin screens as well.

Changes Required

1. Remove the "Home" breadcrumb from all admin screens.
2. Remove non-navigable breadcrumb items — any item that does not have an Angular router link should be removed from the trail.
3. Combine section title + first navigable item into one chip — when a section title (e.g., "Content") precedes a navigable item (e.g., "Search"), both are displayed together as Content: Search, where both parts are clickable and navigate to their respective routes.
4. Audit all admin screens to ensure the complete navigation path is displayed correctly — the new Edit Content screen is a confirmed case; others will be discovered during the audit.

Acceptance Criteria

• The "Home" breadcrumb item is removed from all admin screens that include a breadcrumb component
• Any breadcrumb item that does not have an Angular router link is removed from the breadcrumb trail
• When a section title precedes a navigable item, both are displayed as a single chip in the format "Section: Item" (e.g., "Content: Search"), where both the section name and the item name are clickable and each navigates to its respective route
• An audit of all admin screens confirms no breadcrumb is missing navigable ancestors or showing non-navigable standalone items
• The new Edit Content screen shows the full breadcrumb path reflecting the user's navigation history
• No regressions in existing breadcrumb behavior on other admin screens

Additional Context

The visual change reduces clutter while preserving context: the section label (e.g., "Content") is combined with the section entry point (e.g., "Search") into a single chip separated by a colon. Both parts remain clickable.

Start with the admin breadcrumb component and the new Edit Content screen, then inspect how Angular router links are assigned across admin screens. Audit each breadcrumb against the listed acceptance criteria, including the Section: Item format and clickable routes; done means all admin screens show complete navigable paths without Home or non-navigable standalone items and existing behavior has no regressions.