Remove task-level approval system

Task-level approval (requiresApproval, mergeRequiresApproval,
pending_approval status) was redundant with executionMode
(yolo vs review_per_phase) and blocked the orchestrator's
phase completion flow. Tasks now complete directly;
phase-level review via executionMode is the right granularity.

Removed: schema columns (left in DB, removed from Drizzle),
TaskPendingApprovalEvent, approveTask/listPendingApprovals
procedures, findPendingApproval repository method, and all
frontend approval UI.

apps/server/cli/index.ts

@@ -336,7 +336,7 @@ export function createCli(serverHandler?: (port?: number) => Promise<void>): Com
         }
 
         // Count by status
-        const pending = tasks.filter(t => t.status === 'pending' || t.status === 'pending_approval').length;
+        const pending = tasks.filter(t => t.status === 'pending').length;
         const inProgress = tasks.filter(t => t.status === 'in_progress').length;
         const completed = tasks.filter(t => t.status === 'completed').length;
         const blocked = tasks.filter(t => t.status === 'blocked').length;