feat(app): экраны импорта отчётов, целей, доходов, ребалансировки, налогов и бенчмарков

Импорт (/imports, /instruments/pending) и фаза 4 (/goals, /income,
/rebalance, /tax, аналитика-хаб с benchmarks_card) — по
docs/ai/import-contract.md и docs/ai/phase4-contract.md. file_picker для
загрузки отчёта.

app/lib/features/rebalance/labels.dart

@@ -0,0 +1,14 @@
+import '../portfolio/labels.dart' show assetClassLabels;
+
+/// Bucket labels keyed by the **wire** dimension string.
+///
+/// `features/portfolio/labels.dart` already has `bucketLabel`, but it takes the generated
+/// `AllocationDimension` enum, and the rebalance routes are not in the spec yet — this
+/// layer only has the plain string. Once `just gen-client` produces the enum, this helper
+/// should give way to the existing one.
+String bucketLabelForKey(String dimension, String bucket) {
+  if (bucket == 'cash') return 'Денежные средства';
+  if (bucket == 'unknown') return 'Не указано';
+  if (bucket.isEmpty) return '—';
+  return dimension == 'asset_class' ? (assetClassLabels[bucket] ?? bucket) : bucket;
+}