feat: admin-configurable FINRA download URL

- Add finra_config singleton table (base_url + updated_at)
- Add getFinraBaseUrl() and setFinraBaseUrl() to admin.ts
  Resolution order: DB config > env FINRA_BASE_URL > built-in default
- Add finraConfig query + finraConfigUpdate mutation to admin tRPC router
- Update FinraIngestService.downloadAndIngestFinra to accept optional baseUrl
  param; falls back to getFinraBaseUrl(db) when omitted
- FinraBulkAdapter resolves URL implicitly via the service (no adapter change)
- Add migration #10 for existing DBs

app/server/src/db/schema.sql

@@ -694,3 +694,10 @@ CREATE TABLE IF NOT EXISTS finra_short_interest (
 
 CREATE INDEX IF NOT EXISTS idx_finra_symbol ON finra_short_interest(symbol);
 CREATE INDEX IF NOT EXISTS idx_finra_settlement ON finra_short_interest(settlement_date);
+
+-- FINRA download configuration (admin-configurable URL).
+CREATE TABLE IF NOT EXISTS finra_config (
+  id          TEXT PRIMARY KEY DEFAULT 'singleton',
+  base_url    TEXT NOT NULL DEFAULT 'https://www.finra.org/sites/default/files',
+  updated_at  TEXT NOT NULL
+);