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/coredata/measure.go

@@ -326,6 +326,41 @@ WHERE
 	return count, nil
 }
 
+func (m *Measures) LoadDistinctCategoriesByOrganizationID(
+	ctx context.Context,
+	conn pg.Conn,
+	scope Scoper,
+	organizationID gid.GID,
+) ([]string, error) {
+	q := `
+SELECT DISTINCT
+    category
+FROM
+    measures
+WHERE
+    %s
+    AND organization_id = @organization_id
+ORDER BY
+    category ASC
+`
+	q = fmt.Sprintf(q, scope.SQLFragment())
+
+	args := pgx.NamedArgs{"organization_id": organizationID}
+	maps.Copy(args, scope.SQLArguments())
+
+	rows, err := conn.Query(ctx, q, args)
+	if err != nil {
+		return nil, fmt.Errorf("cannot query measure categories: %w", err)
+	}
+
+	categories, err := pgx.CollectRows(rows, pgx.RowTo[string])
+	if err != nil {
+		return nil, fmt.Errorf("cannot collect measure categories: %w", err)
+	}
+
+	return categories, nil
+}
+
 func (m *Measures) LoadByOrganizationID(
 	ctx context.Context,
 	conn pg.Conn,

pkg/coredata/measure_filter.go

@@ -20,22 +20,25 @@ import (
 
 type (
 	MeasureFilter struct {
-		query *string
-		state *MeasureState
+		query    *string
+		state    *MeasureState
+		category *string
 	}
 )
 
-func NewMeasureFilter(query *string, state *MeasureState) *MeasureFilter {
+func NewMeasureFilter(query *string, state *MeasureState, category *string) *MeasureFilter {
 	return &MeasureFilter{
-		query: query,
-		state: state,
+		query:    query,
+		state:    state,
+		category: category,
 	}
 }
 
 func (f *MeasureFilter) SQLArguments() pgx.NamedArgs {
 	return pgx.NamedArgs{
-		"query": f.query,
-		"state": f.state,
+		"query":    f.query,
+		"state":    f.state,
+		"category": f.category,
 	}
 }
 
@@ -60,6 +63,15 @@ AND
 		ELSE
 			state = @state::mitigation_state
 	END
-		)
+)
+AND
+(
+	CASE
+		WHEN @category::text IS NULL OR @category::text = '' THEN
+			TRUE
+		ELSE
+			category = @category::text
+	END
+)
 	`
 }