feat: Sentinela v0.2.0 — Brazilian Financial Data API in Go

- 20 Go source files, single 16MB binary
- SQLite + FTS5 full-text search (pure Go, no CGO)
- BCB integration: Selic, CDI, IPCA, USD/BRL, EUR/BRL
- CVM integration: 2,524 companies from registry
- Fiber v2 REST API with 42 handlers
- Auto-seeds on first run (~5s for BCB + CVM)
- Token bucket rate limiter, optional API key auth
- Periodic sync scheduler (configurable)
- Graceful shutdown, structured logging (slog)
- All endpoints tested with real data

internal/db/sqlite.go

@@ -0,0 +1,52 @@
+package db
+
+import (
+	"database/sql"
+	"fmt"
+	"log/slog"
+	"os"
+	"path/filepath"
+
+	_ "modernc.org/sqlite"
+)
+
+type DB struct {
+	Conn *sql.DB
+}
+
+func New(dbPath string) (*DB, error) {
+	dir := filepath.Dir(dbPath)
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		return nil, fmt.Errorf("create db dir: %w", err)
+	}
+
+	conn, err := sql.Open("sqlite", dbPath+"?_journal_mode=WAL&_busy_timeout=5000")
+	if err != nil {
+		return nil, fmt.Errorf("open db: %w", err)
+	}
+
+	conn.SetMaxOpenConns(1) // SQLite single-writer
+
+	if _, err := conn.Exec(schema); err != nil {
+		return nil, fmt.Errorf("run schema: %w", err)
+	}
+
+	slog.Info("database initialized", "path", dbPath)
+	return &DB{Conn: conn}, nil
+}
+
+func (d *DB) Close() error {
+	return d.Conn.Close()
+}
+
+func (d *DB) IsEmpty() bool {
+	var count int
+	d.Conn.QueryRow("SELECT COUNT(*) FROM companies").Scan(&count)
+	return count == 0
+}
+
+func (d *DB) IsMarketEmpty() bool {
+	var count int
+	d.Conn.QueryRow("SELECT COUNT(*) FROM selic_history").Scan(&count)
+	return count == 0
+}