Refactor MeasuresPage to use Relay fragments

Replace the client-side grouped-by-category view (fetching 500 items)
with a flat table using server-side filtering and cursor-based
pagination. Colocate GraphQL queries, fragments, and mutations in the
component file per console CLAUDE.md conventions.

Backend changes add a category filter to the measure list endpoints
(GraphQL, MCP) and a new measureCategories field on Organization.

Signed-off-by: Bryan Frimin <bryan@getprobo.com>

pkg/server/api/mcp/v1/specification.yaml

@@ -1434,6 +1434,9 @@ components:
             state:
               $ref: "#/components/schemas/MeasureState"
               description: Measure state filter
+            category:
+              type: string
+              description: Filter by measure category
 
     ListMeasuresOutput:
       type: object