Add event-sourced wallet and transaction tracking system

Wallets table with 7 seeded wallets, events table for three transaction
types (bank_to_exchange, exchange_to_wallet, wallet_to_wallet). Balances
computed from event credits/debits in sats. REST endpoints for CRUD.

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

resources/migrations/20260307000000-create-wallets.up.sql

@@ -0,0 +1,9 @@
+CREATE TABLE wallets (
+  id         UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  name       TEXT NOT NULL UNIQUE,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+--;;
+INSERT INTO wallets (name) VALUES
+  ('Crypto.Com'), ('Nexo'), ('CoinCorner'), ('Strike'),
+  ('Cold'), ('Coldcard'), ('Nunchuk Multi Sig');