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/test/integration/full-flow/report.ts

@@ -69,7 +69,7 @@ export function printDetailResult(phase: Phase, tasks: Task[]): void {
   console.log(`\n[DETAIL] Phase "${phase.name}" → ${tasks.length} task(s)`);
   console.log(THIN);
   tasks.forEach((t, i) => {
-    const flags = [t.category, t.type, t.requiresApproval ? 'approval-required' : 'auto'].join(', ');
+    const flags = [t.category, t.type].join(', ');
     line(`${i + 1}. ${t.name} [${flags}]`);
     if (t.description) {
       line(`   ${t.description.slice(0, 120)}`);