feat: add legacy config migration + test

internal/core/appsettings/manager.go

@@ -61,6 +61,7 @@ func NewDefaultManager() *Manager {
 }
 
 // Load reads app settings from disk, creating defaults if missing.
+// Supports migration from legacy v1 config format (vault_path field).
 func (m *Manager) Load() error {
 	m.mu.Lock()
 	defer m.mu.Unlock()
@@ -74,6 +75,26 @@ func (m *Manager) Load() error {
 		return fmt.Errorf("failed to read app settings: %w", err)
 	}
 
+	// Try to detect legacy format (has "vault_path" instead of "currentVaultPath")
+	var raw map[string]interface{}
+	if err := json.Unmarshal(data, &raw); err == nil {
+		if _, hasLegacy := raw["vault_path"]; hasLegacy {
+			// Legacy v1 config — migrate
+			m.config = defaultConfig()
+			if vp, ok := raw["vault_path"].(string); ok && vp != "" {
+				m.config.CurrentVaultPath = vp
+			}
+			if theme, ok := raw["theme"].(string); ok && theme != "" {
+				m.config.Theme = theme
+			}
+			// Save migrated config
+			if err := m.saveLocked(); err != nil {
+				return fmt.Errorf("failed to save migrated config: %w", err)
+			}
+			return nil
+		}
+	}
+
 	var cfg Config
 	if err := json.Unmarshal(data, &cfg); err != nil {
 		// Corrupt config: backup and create defaults

internal/core/appsettings/manager_test.go

@@ -131,3 +131,35 @@ func TestAppSettings_NotInsideVault(t *testing.T) {
 		t.Errorf("app settings path should be under .config/verstak, got %s", path)
 	}
 }
+
+func TestLoad_LegacyMigration(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "config.json")
+
+	// Write a legacy v1 config
+	legacy := `{
+  "version": 1,
+  "vault_path": "/home/user/Documents/MyVault",
+  "theme": "light",
+  "first_run_completed": true
+}`
+	if err := os.WriteFile(path, []byte(legacy), 0o600); err != nil {
+		t.Fatalf("write legacy config: %v", err)
+	}
+
+	m := NewManager(path)
+	if err := m.Load(); err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+
+	cfg := m.Get()
+	if cfg.CurrentVaultPath != "/home/user/Documents/MyVault" {
+		t.Errorf("CurrentVaultPath: got %q, want %q", cfg.CurrentVaultPath, "/home/user/Documents/MyVault")
+	}
+	if cfg.Theme != "light" {
+		t.Errorf("Theme: got %q, want %q", cfg.Theme, "light")
+	}
+	if cfg.SchemaVersion != 1 {
+		t.Errorf("SchemaVersion: got %d, want 1", cfg.SchemaVersion)
+	}
+}