feat(CF-314): Add planning_mode_required field and smart planning mode support

Adds DB column, TypeScript types, MCP tool schemas, and CRUD handlers
for planning_mode_required (NULL=auto-detect, true=always, false=never).

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

src/types.ts

@@ -10,6 +10,7 @@ export interface Task {
   priority: 'P0' | 'P1' | 'P2' | 'P3';
   version_id?: string;
   epic_id?: string;
+  planning_mode_required?: boolean | null;
   created_at: Date;
   updated_at: Date;
   completed_at?: Date;