Docs: Missing Context Center documentation for v2.0.x-SNAPSHOT

[kiran1287]

Problem

The v2.0.x-SNAPSHOT docs had no documentation for Context Center (Articles, Memories, Documents, and the Dashboard landing page), even though it's a real OSS feature already referenced by the search_company_context, get_company_context, and create_context_memory MCP tools in how-to-guides/mcp/reference.mdx. There was also no mention of it on the How-to Guides home page or the v2.0.x-SNAPSHOT homepage's "What's New" section, and no callout for the newly added Prefect and Omni connectors.

Fix

• New "Context Center" section: overview, Articles, Memories, Documents (with the Dashboard landing page documented under Overview)
• New top-level "Context Center" nav tab, parallel to Data Discovery, Data Contracts, and Data Collaboration
• "Context Center" card added to the How-to Guides home page
• "Context Center" and "New Connectors" (Prefect, Omni) cards added to the v2.0.x-SNAPSHOT homepage "What's New" section
• Content and screenshots verified against OpenMetadata source (contextMemory.json schema, RBAC resource categories, ContextCenter* UI routes)

Fixed by #392.