feat: add question export foundation

supabase/migrations/202606290015_content_export_jobs.sql

@@ -0,0 +1,44 @@
+create table if not exists public.content_export_jobs (
+  id uuid primary key default gen_random_uuid(),
+  tenant_id uuid not null references public.tenants(id) on delete cascade,
+  created_by uuid references public.platform_users(id) on delete set null,
+  export_type text not null default 'questions'
+    check (export_type in ('questions', 'paper', 'daily_practice')),
+  format text not null default 'json'
+    check (format in ('json', 'paper_json', 'print_payload')),
+  scope_type text not null
+    check (scope_type in ('collection', 'entry', 'content_node')),
+  scope_id uuid not null,
+  status text not null default 'completed'
+    check (status in ('completed', 'failed')),
+  include_answers boolean not null default true,
+  include_explanations boolean not null default true,
+  include_video_refs boolean not null default false,
+  question_count integer not null default 0 check (question_count >= 0),
+  summary jsonb not null default '{}'::jsonb,
+  options jsonb not null default '{}'::jsonb,
+  output_metadata jsonb not null default '{}'::jsonb,
+  error_message text,
+  finished_at timestamptz,
+  created_at timestamptz not null default now(),
+  updated_at timestamptz not null default now()
+);
+
+create index if not exists idx_content_export_jobs_tenant_created
+  on public.content_export_jobs(tenant_id, created_at desc);
+
+create index if not exists idx_content_export_jobs_scope
+  on public.content_export_jobs(tenant_id, scope_type, scope_id, created_at desc);
+
+alter table public.content_export_jobs enable row level security;
+
+drop policy if exists tenant_isolation on public.content_export_jobs;
+create policy tenant_isolation on public.content_export_jobs
+  for all
+  using (tenant_id = app.current_tenant_id() or app.is_platform_admin())
+  with check (tenant_id = app.current_tenant_id() or app.is_platform_admin());
+
+drop trigger if exists set_updated_at on public.content_export_jobs;
+create trigger set_updated_at
+  before update on public.content_export_jobs
+  for each row execute function app.touch_updated_at();