feat(webhooks): paginate list + call-history endpoints (server + web UI) (#1268)

Add total-count pagination to the webhook admin endpoints and the web UI.

Store:
- WebhookStore/WebhookCallStore gain Count; WebhookListFilter gains
  IncludeRevoked + Query (PG + SQLite, parameterized, tenant-scoped)

API:
- GET /v1/webhooks and GET /v1/webhooks/{id}/calls return
  {items, total, limit, offset} with server-side search + revoked filtering

Web UI:
- server-driven list pager + search/revoked filter; call-history dialog uses
  the real total (fixes the full-page "has more" boundary bug)
- i18n pager labels (en/vi/zh)

Tests: store pagination integration test; mock stores implement Count.
No schema migration (read-only COUNT).

internal/webhooks/worker_test.go

@@ -94,6 +94,9 @@ func (s *stubCallStore) ClaimNext(_ context.Context, _ uuid.UUID, _ time.Time) (
 func (s *stubCallStore) List(_ context.Context, _ store.WebhookCallListFilter) ([]store.WebhookCallData, error) {
 	return nil, nil
 }
+func (s *stubCallStore) Count(_ context.Context, _ store.WebhookCallListFilter) (int, error) {
+	return 0, nil
+}
 func (s *stubCallStore) DeleteOlderThan(_ context.Context, _ uuid.UUID, _ time.Time) (int64, error) {
 	return 0, nil
 }
@@ -119,6 +122,9 @@ func (s *stubWebhookStore) GetByHash(_ context.Context, _ string) (*store.Webhoo
 func (s *stubWebhookStore) List(_ context.Context, _ store.WebhookListFilter) ([]store.WebhookData, error) {
 	return nil, nil
 }
+func (s *stubWebhookStore) Count(_ context.Context, _ store.WebhookListFilter) (int, error) {
+	return 0, nil
+}
 func (s *stubWebhookStore) Update(_ context.Context, _ uuid.UUID, _ map[string]any) error { return nil }
 func (s *stubWebhookStore) RotateSecret(_ context.Context, _ uuid.UUID, _, _, _ string) error {
 	return nil