feat(09-02): add shortcuts config package with default bindings and Wails persistence

- Create backend/shortcuts/config.go with DefaultBindings(), ApplyDefaults(), Validate()
- Wire Shortcuts field into main Config struct with TOML persistence
- Add GetShortcuts, SetShortcuts, SetShortcut, ResetShortcuts Wails binding methods
- Regenerate Wails TypeScript bindings for new config methods
- Fix wsl lint in library.go (blank line before logger call)

backend/library/library.go

@@ -590,6 +590,7 @@ func (l *Library) Scan() (*ScanMetrics, error) {
 
 	if cancelled {
 		metrics.Cancelled = true
+
 		l.logger.Info("scan cancelled, skipping orphan cleanup")
 	} else {
 		// --- Phase 5: orphan cleanup ---