Remove 'Browse Resources' sidebar group and promote 'Tips & Triks' to standalone section

## As a user of the Learning Hub
## I want to see a clean, non-duplicated sidebar navigation
## So that I can navigate content without confusion caused by redundant links

## Business Goal
The Learning Hub sidebar currently contains a "Browse Resources" group whose child links duplicate the navigation already available under the "Verktøy" section of the site. Removing this duplication reduces confusion, simplifies the sidebar, and improves wayfinding. Additionally, "Tips & Triks" (currently nested inside "Browse Resources") needs to have its own section at the bottom of the list.

## Acceptance Criteria
- The "Browse Resources" sidebar group is removed from the Learning Hub sidebar
- The "Tips & Triks" section (with all its child links) is promoted to a standalone sidebar group
- The "Tips & Triks" group appears at the bottom of the sidebar navigation list (below "Hands-on")
- No other sidebar groups (Fundamentals, Reference, Hands-on) are affected
- All existing "Tips & Triks" child pages remain accessible and functional

## Prerequisites
⚠️ Prerequisite: Confirm which Browse Resources child links (Home, Agents, Instructions, Skills, Hooks, Workflows, Plugins, Tools, Contributors) can be safely removed without breaking navigation elsewhere — Owner: Roberto

## Dependencies
- Part of Epic 1 — Foundation & Design System #38

## Estimate
0.5 days