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/agent/file-io.test.ts

@@ -48,7 +48,6 @@ describe('writeInputFiles', () => {
       id: 'init-1',
       name: 'Test Initiative',
       status: 'active',
-      mergeRequiresApproval: true,
       branch: 'cw/test-initiative',
       executionMode: 'review_per_phase',
       createdAt: new Date('2026-01-01'),

apps/server/agent/file-io.ts

@@ -132,7 +132,6 @@ export async function writeInputFiles(options: WriteInputFilesOptions): Promise<
         id: ini.id,
         name: ini.name,
         status: ini.status,
-        mergeRequiresApproval: ini.mergeRequiresApproval,
         branch: ini.branch,
       },
       '',