FE-PR-005: Remove story from task creation - restricted to Proposal Accept only

- Remove 'story' type from TASK_TYPES in CreateTaskPage.tsx and CreateTaskModal.tsx
- All story/* task types now only creatable via Proposal Accept workflow
- Added comments explaining the restriction

src/components/CreateTaskModal.tsx

@@ -3,7 +3,7 @@ import api from '@/services/api'
 import type { Milestone, Project, Task } from '@/types'
 
 const TASK_TYPES = [
-  { value: 'story', label: 'Story', subtypes: ['improvement', 'refactor'] },  // P9.6: 'feature' removed — must come from proposal accept
+  // P9.6: 'story' removed — all story/* types are restricted; must come from Proposal Accept workflow
   { value: 'issue', label: 'Issue', subtypes: ['infrastructure', 'performance', 'regression', 'security', 'user_experience', 'defect'] },
   // P7.1: 'task' type removed — defect subtype migrated to issue/defect
   { value: 'test', label: 'Test', subtypes: ['regression', 'security', 'smoke', 'stress'] },

src/pages/CreateTaskPage.tsx

@@ -4,7 +4,7 @@ import api from '@/services/api'
 import type { Project, Milestone } from '@/types'
 
 const TASK_TYPES = [
-  { value: 'story', label: 'Story', subtypes: ['improvement', 'refactor'] },  // P9.6: 'feature' removed — must come from proposal accept
+  // P9.6: 'story' removed — all story/* types are restricted; must come from Proposal Accept workflow
   { value: 'issue', label: 'Issue', subtypes: ['infrastructure', 'performance', 'regression', 'security', 'user_experience', 'defect'] },
   // P7.1: 'task' type removed — defect subtype migrated to issue/defect
   { value: 'test', label: 'Test', subtypes: ['regression', 'security', 'smoke', 'stress'] },