Add task priority field

Introduce a rank-style priority on tasks, scoped by
(organization_id, state). New tasks auto-assign the next
priority. Reordering uses the same CTE-based algorithm as
trust center references and compliance external URLs.
Exposed through GraphQL, MCP, and the PRIORITY order field.

Signed-off-by: Sacha Al Himdani <sacha@getprobo.com>

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

@@ -4619,6 +4619,7 @@ components:
     TaskOrderField:
       type: string
       enum:
+        - PRIORITY
         - CREATED_AT
       go.probo.inc/mcpgen/type: go.probo.inc/probo/pkg/coredata.TaskOrderField
 
@@ -4642,6 +4643,7 @@ components:
         - organization_id
         - name
         - state
+        - priority
         - created_at
         - updated_at
       properties:
@@ -4671,6 +4673,9 @@ components:
         state:
           $ref: "#/components/schemas/TaskState"
           description: Task state
+        priority:
+          type: integer
+          description: Task priority within state
         time_estimate:
           anyOf:
             - $ref: "#/components/schemas/Duration"
@@ -4822,6 +4827,9 @@ components:
             - type: "null"
               description: No state
           description: Task state
+        priority:
+          type: integer
+          description: Task priority within state
         time_estimate:
           anyOf:
             - $ref: "#/components/schemas/Duration"