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/drizzle/0030_remove_task_approval.sql

@@ -0,0 +1,6 @@
+-- Migrate any pending_approval tasks to completed (unblock the pipeline)
+UPDATE tasks SET status = 'completed' WHERE status = 'pending_approval';
+
+-- Note: SQLite cannot drop columns. The merge_requires_approval column on
+-- initiatives and requires_approval column on tasks are left in the DB but
+-- removed from the Drizzle schema. Drizzle ignores extra DB columns.

apps/server/drizzle/meta/_journal.json

@@ -211,6 +211,13 @@
       "when": 1772064000000,
       "tag": "0029_add_project_last_fetched_at",
       "breakpoints": true
+    },
+    {
+      "idx": 30,
+      "version": "6",
+      "when": 1772150400000,
+      "tag": "0030_remove_task_approval",
+      "breakpoints": true
     }
   ]
 }