feat(navigation): implement contextual back navigation for Neuron's page

[yhabib]

Motivation

The Neuron's page has two potential entry points:

• The Staking page, accessed by clicking on any row in the ProjectsTable.
• The Portfolio page, accessed by clicking on any of the stake tokens (feat(portfolio): add authenticated neurons navigation from top projects #6342).

This PR follows up on #6343 by redirecting users from the Neuron's page based on their entry method.

Changes

• Uses the new store neuronsPageOrigin to determine the navigation point when returning from the Neurons page.

Tests

• Split the current test into a check button and a navigation check that returns to the Staking page.
• Add a unit test to verify that navigation is correct when coming from the Portfolio page.

Todos

• Add entry to changelog (if necessary).
  Not necessary