Phase 1: database schema, migrations, repository, user seeding

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

internal/db/db.go

@@ -0,0 +1,57 @@
+package db
+
+import (
+	"database/sql"
+	_ "embed"
+	"fmt"
+
+	_ "modernc.org/sqlite"
+
+	"golang.org/x/crypto/bcrypt"
+	"qbank/internal/config"
+)
+
+//go:embed schema.sql
+var schema string
+
+func Open(path string) (*sql.DB, error) {
+	db, err := sql.Open("sqlite", path)
+	if err != nil {
+		return nil, fmt.Errorf("open sqlite: %w", err)
+	}
+	db.SetMaxOpenConns(1)
+	for _, stmt := range []string{
+		"PRAGMA journal_mode=WAL",
+		"PRAGMA foreign_keys=ON",
+	} {
+		if _, err := db.Exec(stmt); err != nil {
+			db.Close()
+			return nil, fmt.Errorf("pragma %q: %w", stmt, err)
+		}
+	}
+	if _, err := db.Exec(schema); err != nil {
+		db.Close()
+		return nil, fmt.Errorf("apply schema: %w", err)
+	}
+	return db, nil
+}
+
+func Seed(db *sql.DB, users []config.AdminUser) error {
+	var count int
+	if err := db.QueryRow("SELECT COUNT(*) FROM users").Scan(&count); err != nil {
+		return fmt.Errorf("count users: %w", err)
+	}
+	if count > 0 {
+		return nil
+	}
+	for _, u := range users {
+		hash, err := bcrypt.GenerateFromPassword([]byte(u.Password), bcrypt.DefaultCost)
+		if err != nil {
+			return fmt.Errorf("hash password for %q: %w", u.Name, err)
+		}
+		if _, err := db.Exec("INSERT INTO users (name, password_hash) VALUES (?, ?)", u.Name, string(hash)); err != nil {
+			return fmt.Errorf("insert user %q: %w", u.Name, err)
+		}
+	}
+	return nil
+}