feat(statements+analytics): normalise statement_type; fix analytics scoping

Groundwork for importing bank and loan statements alongside credit cards.

statement_type was whatever free text Gemini put in account_type ('Credit Card',
'credit card', 'credit_card', 'Business Card', 'ACCESS ADVANTAGE',
'multi-currency account'). The UI coped only by doing .includes("card"), which
breaks as soon as bank and loan statements arrive.

- Migration 0013 adds normalize_statement_type() + a BEFORE INSERT/UPDATE
  trigger and a CHECK constraint over credit_card|transaction|savings|loan|
  offset|investment|other. The trigger means the N8N workflow keeps working
  unchanged while it still sends free text. Raw value stays in account_type.
  Backfilled 99 existing rows.
- src/lib/statement-types.ts mirrors the vocabulary for the UI; statements page
  now filters by the real types and headlines balance vs amount due per type.

Analytics were scoped with INNER JOIN statements + s.owner_id, which silently
dropped all 180 manual/CSV transactions (statement_id IS NULL) from every
report. Switched all six routes to LEFT JOIN + COALESCE(t.owner_id, s.owner_id)
via shared fragments in src/lib/analytics-sql.ts, so the transfers/investment
exclusion that stops card-payment double counting stays consistent. Also
extended that exclusion to trip analytics, which had none.

Drive-by: /api/analytics/subscriptions was returning 500 on an unserialisable
BigInt from COUNT(*) + 1.

Verified against the live DB: monthly spend picks up the previously invisible
manual transactions (Apr 9,849.91 -> 14,286.70) and all four analytics
endpoints return 200.

src/app/api/analytics/merchants/[merchant]/route.ts

@@ -1,6 +1,7 @@
 import { NextRequest, NextResponse } from "next/server";
 import { getCurrentUser } from "@/lib/auth";
 import { queryRaw } from "@/lib/db";
+import { OWNER_SCOPE, STATEMENTS_JOIN } from "@/lib/analytics-sql";
 
 export async function GET(
   req: NextRequest,
@@ -38,13 +39,13 @@ export async function GET(
       END::numeric(10,2) as my_amount,
       t.transaction_type,
       COALESCE(o.category_override, t.category) as category,
-      s.bank_name,
+      COALESCE(s.bank_name, 'Manual') as bank_name,
       t.statement_id
     FROM transactions t
-    JOIN statements s ON s.id = t.statement_id
+    ${STATEMENTS_JOIN}
     LEFT JOIN transaction_overrides o ON o.transaction_id = t.id
     LEFT JOIN transaction_splits ts ON ts.transaction_id = t.id AND ts.participant_id = $1
-    WHERE s.owner_id = $1
+    WHERE ${OWNER_SCOPE} = $1
       AND t.transaction_type IN ('debit', 'fee', 'interest', 'refund', 'credit')
       AND COALESCE(o.merchant_normalized, t.merchant_normalized, t.merchant_name, t.description) = $2
     ORDER BY t.transaction_date DESC