[Feature]: Estate: Search Integration for Remote Entities

Parent PRD

#143

What to build

Extend the search system so remote entities appear inline in search results with proper remote metadata, enabling cross-instance discovery.

• Extend SearchIndexItem with is_remote: bool, source_instance_id: Optional[str], source_instance_name: Optional[str] fields
• Update SearchManager.build_index() to query RemoteEntityMetadataDb and populate remote fields on index items for imported entities
• No ranking bias between local and remote results
• Update /api/search response to include the new fields

See "Search Integration" section of the parent PRD.

Acceptance criteria

• SearchIndexItem has is_remote, source_instance_id, source_instance_name fields
• Remote entities appear in search results with is_remote=True and source metadata populated
• Local entities continue to work unchanged (is_remote=False or None)
• No ranking bias between local and remote results
• Stale remote entities are excluded from search (or shown with stale indicator)
• Tests: extend test_search_manager.py with remote entity scenarios

Blocked by

• Blocked by #145 (Remote Entity Metadata)
• Blocked by #150 (Import Sync Service)

User stories addressed

• User story 9, 10, 24

Start with the Search Integration section of parent PRD #143, after reviewing blocked issues #145 and #150. Trace SearchIndexItem, SearchManager.build_index(), RemoteEntityMetadataDb, and the /api/search response, then extend test_search_manager.py with remote scenarios. Done means remote metadata appears without ranking bias, local results remain unchanged, and stale entities follow the agreed behavior.