[Bug]: Contract-property / contract-schema semantic links are not navigable

Summary

Clicking a contract-property (or contract-schema) semantic link in the Linked objects panel always fails with "Cannot navigate to data_contract_property" — these entity types have no navigation handler.

Steps to reproduce

1. Open a concept that is linked to a data_contract_property (or data_contract_schema).
2. Click the linked object in the Linked objects panel.

Expected: navigate to the contract property/schema (e.g. the parent contract's schema view, anchored to the property).
Actual: a destructive error toast: "Cannot navigate to data_contract_property".

Root cause (traced)

src/frontend/src/components/semantic/linked-objects-panel.tsx:287-325 — navigateToEntity has case branches for data_product, data_contract, asset, data_domain, and uc_catalog/uc_schema/uc_table/uc_column, but no case for data_contract_property or data_contract_schema. Those fall through to the default branch (error toast).

Note: these two entity types are handled elsewhere in the same file (icon map at :76-77, colour map at :91-92, and the schema/property detail branches at :148-173), so navigation is the only gap.

PR #596 touches this file but does not add these navigation cases.

Suggested fix

Add case 'data_contract_schema' and case 'data_contract_property' to navigateToEntity, routing to the parent contract's detail view (the composite id encodes {contract_id}#{schema}[#{property}], so the contract id can be parsed out and the schema/property used as an anchor/highlight).

Start in src/frontend/src/components/semantic/linked-objects-panel.tsx, reading navigateToEntity around lines 287-325 alongside the schema/property detail branches at lines 148-173. Add navigation coverage for data_contract_schema and data_contract_property using the composite id described in the issue; done means linked objects open the parent contract schema view with the schema or property targeted instead of showing the error toast.