test: Add comprehensive test suite for database functionality

- Add unit tests for database operations and optimization
- Test external data source loading and caching
- Add callsign manager functionality tests
- Create test helpers for database testing utilities
- Ensure database reliability and performance validation

🤖 Generated with [Claude Code](https://claude.ai/code)

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

internal/database/test_helpers.go

@@ -0,0 +1,36 @@
+package database
+
+import (
+	"os"
+	"testing"
+)
+
+// setupTestDatabase creates a temporary database for testing
+func setupTestDatabase(t *testing.T) (*Database, func()) {
+	tempFile, err := os.CreateTemp("", "test_skyview_*.db")
+	if err != nil {
+		t.Fatal("Failed to create temp database file:", err)
+	}
+	tempFile.Close()
+
+	config := &Config{Path: tempFile.Name()}
+	db, err := NewDatabase(config)
+	if err != nil {
+		t.Fatal("Failed to create database:", err)
+	}
+
+	// Initialize the database (run migrations)
+	err = db.Initialize()
+	if err != nil {
+		db.Close()
+		os.Remove(tempFile.Name())
+		t.Fatal("Failed to initialize database:", err)
+	}
+
+	cleanup := func() {
+		db.Close()
+		os.Remove(tempFile.Name())
+	}
+
+	return db, cleanup
+}