feat: consolidate Team and Ownership model

[larsgeorge-db]

Summary

• Consolidates the disparate "people" surfaces (ODCS/ODPS Team, Ontos Team entity, Business Owners) into a single authoritative Owners panel with read-only provenance for imported data
• Renames misleading "Owner:" label to "Team:" in metadata grid and groups it with Project
• Merges active Business Owners into YAML export team section for standards compliance
• Adds sidebar fallback indicator and removes dead "Import from Team" flow

Changes

Frontend

• OwnershipPanel: Extended with "Imported Contacts" collapsible section, "Copy from Team" dialog
• data-product-details.tsx: Sidebar Contacts fallback indicator, removed old import flow
• data-contract-details.tsx: Read-only ODCS Team Metadata section, removed old import flow
• Both detail pages: "Owner:" → "Team:" label rename, Project/Team grouping

Backend

• business_owners_routes.py: New POST /api/business-owners/import-from-team endpoint
• data_contracts_manager.py: YAML export merges Business Owners into team section
• data_products_manager.py: Same merge logic for ODPS export

Docs

• PRD with resolved design decisions: docs/prds/prd-consolidate-team-and-ownership.md

Test plan

• Verified via Playwright: "Team:" label on both pages
• Verified: "Copy from Team" dialog opens and lists team members
• Verified: Imported Contacts section expands with correct layout
• Verified: Sidebar shows "From imported data" indicator on fallback
• Verified: ODCS export includes merged Business Owners in team section
• Backend unit tests for import-from-team endpoint
• Backend unit tests for export merge dedup logic

Closes #431