docs: bump version to 5.7.0 and update documentation

- marketplace.json: 5.6.0 → 5.7.0
- data-platform plugin.json: 1.1.0 → 1.3.0
- CHANGELOG.md: Add v5.7.0 entry with data-platform additions
- README.md: Update Domain Advisory table (Data: planned → active)

Domain Advisory Pattern now fully operational for both domains.

Closes #377

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

README.md

@@ -153,7 +153,7 @@ The marketplace supports cross-plugin domain advisory integration:
 | Domain | Plugin | Gate Command |
 |--------|--------|--------------|
 | Visualization | viz-platform | `/design-gate` |
-| Data (planned) | data-platform | `/data-gate` |
+| Data | data-platform | `/data-gate` |
 
 ## MCP Servers