[Housekeeping]: Use NetBox’s default `get_absolute_url()` implementation

[pheus]

Proposed Changes

• Drop custom get_absolute_url() methods from plugin models and use the default from NetBox.
• Verify that generated object detail URLs remain unchanged/compatible.

Justification

• Reduce custom code and maintenance burden.
• Align with current NetBox core capabilities.

References

• Related PR: Use default absolute model URL #269