Add recurring transaction detection, subscriptions page, and UK tax reporting

- Recurring service: auto-detects direct debits/subscriptions from CSV imports
  using frequency analysis; manual toggle in transaction detail drawer
- Subscriptions page (/subscriptions): groups recurring payments with monthly
  cost equivalents, next-payment badges, and re-scan trigger
- UK Tax page (/tax): payslips/P60 entry, income tax + NI + CGT + dividend tax
  calculations, configurable rate tables per tax year (pre-seeded 2024/25 and
  2025/26), editable in-app so Budget changes need no rebuild
- Migration 0006: tax_rate_configs, tax_profiles, payslips, manual_cgt_disposals
  with RLS; seeds 2025/2026 rate configs for existing users
- Chart tooltip fix: all Recharts tooltips now use TOOLTIP_STYLE constant so
  they render correctly across all dark/light themes

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/services/transaction_service.py

@@ -47,6 +47,7 @@ def _to_response(t: Transaction) -> dict:
         "notes": _dec(t.notes_enc),
         "tags": t.tags or [],
         "is_recurring": t.is_recurring,
+        "recurring_rule": t.recurring_rule,
         "attachment_refs": t.attachment_refs or [],
         "created_at": t.created_at,
         "updated_at": t.updated_at,
@@ -221,6 +222,10 @@ async def update_transaction(
         txn.notes_enc = _enc(data.notes)
     if data.tags is not None:
         txn.tags = data.tags
+    if data.is_recurring is not None:
+        txn.is_recurring = data.is_recurring
+    if data.recurring_rule is not None:
+        txn.recurring_rule = data.recurring_rule
 
     txn.updated_at = now
     await db.flush()
@@ -307,5 +312,7 @@ async def import_csv(
     await db.flush()
     if imported > 0:
         await recalculate_balance(db, account_id)
+        from app.services.recurring_service import detect_recurring
+        await detect_recurring(db, user_id)
 
     return {"imported": imported, "skipped": skipped}