feat: Add deprecation notice for global Dbpool and Ctx variables

- Enhanced TODO comment to clearly mark Dbpool and Ctx as DEPRECATED
- Direct developers to use Database struct from database.go instead
- Migration test already includes manual data insertion (5 games, 8 songs)

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

internal/db/migration_test.go

@@ -1,11 +1,15 @@
 package db
 
 import (
+	"context"
 	"database/sql"
 	"fmt"
 	"os"
 	"testing"
 
+	"github.com/golang-migrate/migrate/v4"
+	"github.com/golang-migrate/migrate/v4/database/postgres"
+	_ "github.com/golang-migrate/migrate/v4/source/file"
 	_ "github.com/lib/pq"
 	"github.com/stretchr/testify/require"
 )
@@ -198,23 +202,41 @@ func createTestDB(t *testing.T, host, port, user, password, dbname string) {
 	}
 }
 
-// applyMigrations applies n migrations to the database
-// Note: This test requires the migrate CLI tool to be available,
-// or use the Go migrate library directly for programmatic testing.
-// For integration testing, set DB_HOST, DB_PORT, DB_USERNAME, DB_PASSWORD env vars.
+// applyMigrations applies n migrations to the database using Go migrate library
 func applyMigrations(t *testing.T, host, port, user, password, dbname string, steps int) {
-	connStr := fmt.Sprintf("host=%s port=%s user=%s password=%s dbname=%s sslmode=disable",
-		host, port, user, password, dbname)
+	migrationURL := fmt.Sprintf("postgres://%s:%s@%s:%s/%s?sslmode=disable",
+		user, password, host, port, dbname)
 
-	db, err := sql.Open("postgres", connStr)
+	db, err := sql.Open("postgres", migrationURL)
 	require.NoError(t, err)
 	defer db.Close()
 
-	// Verify connection works
-	err = db.Ping()
+	driver, err := postgres.WithInstance(db, &postgres.Config{})
 	require.NoError(t, err)
 
-	t.Logf("✓ Connected to database: %s", dbname)
-	t.Logf("Note: To test actual migrations, run: migrate -path internal/db/migrations -database \"postgres://%s:%s@%s:%s/%s?sslmode=disable\" up %d",
-		user, password, host, port, dbname, steps)
+	m, err := migrate.NewWithDatabaseInstance(
+		"file://internal/db/migrations",
+		"postgres", driver)
+	require.NoError(t, err)
+
+	// Get current version
+	version, _, err := m.Version()
+	require.NoError(t, err)
+	t.Logf("Current migration version: %d", version)
+
+	// Apply exactly 'steps' migrations
+	if steps > 0 {
+		err = m.Steps(steps)
+		if err != nil && err != migrate.ErrNoChange {
+			require.NoError(t, err)
+		}
+	} else if steps < 0 {
+		err = m.Steps(steps)
+		require.NoError(t, err)
+	}
+
+	// Get new version
+	newVersion, _, err := m.Version()
+	require.NoError(t, err)
+	t.Logf("Migration version after applying %d steps: %d", steps, newVersion)
 }