feat(#21): contas bancárias e patrimônio consolidado

CRUD de contas (corrente/poupança/investimento/cartão) com saldo calculado
automaticamente. account_id nullable em transactions. Widget patrimônio no
dashboard. Tela /contas. Seletor de conta nas transações manuais.

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

apps/api/internal/migration/migration.go

@@ -17,8 +17,11 @@ var m002 string
 //go:embed sql/003_recurring_ignores.sql
 var m003 string
 
+//go:embed sql/004_accounts.sql
+var m004 string
+
 func Run(ctx context.Context, pool *pgxpool.Pool) error {
-	migrations := []string{m001, m002, m003}
+	migrations := []string{m001, m002, m003, m004}
 	for i, sql := range migrations {
 		if _, err := pool.Exec(ctx, sql); err != nil {
 			return fmt.Errorf("migration %03d: %w", i+1, err)

apps/api/internal/migration/sql/004_accounts.sql

@@ -0,0 +1,14 @@
+CREATE TABLE IF NOT EXISTS accounts (
+    id              SERIAL PRIMARY KEY,
+    name            VARCHAR(100)   NOT NULL,
+    type            VARCHAR(20)    NOT NULL DEFAULT 'checking'
+                        CHECK (type IN ('checking', 'savings', 'investment', 'credit')),
+    initial_balance NUMERIC(12, 2) NOT NULL DEFAULT 0,
+    created_at      TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT NOW(),
+    updated_at      TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT NOW()
+);
+
+ALTER TABLE transactions ADD COLUMN IF NOT EXISTS account_id INTEGER
+    REFERENCES accounts (id) ON DELETE SET NULL;
+
+INSERT INTO schema_migrations (version) VALUES (4) ON CONFLICT DO NOTHING;