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/shortcuts/config.go

@@ -0,0 +1,64 @@
+// Package shortcuts manages keyboard shortcut configuration.
+package shortcuts
+
+// Config holds user-customized keyboard shortcut bindings.
+// Keys are action IDs (e.g. "player.playPause"), values are
+// key combo strings in canonical format (e.g. "Ctrl+F", "Space").
+type Config struct {
+	Bindings map[string]string `toml:"Bindings"`
+}
+
+// DefaultBindings returns the default keyboard shortcut bindings.
+// Follows hybrid style: Space/arrows for player, Ctrl+key for app actions.
+func DefaultBindings() map[string]string {
+	return map[string]string{
+		// Player controls (Global scope, no modifier)
+		"player.playPause":   "Space",
+		"player.next":        "N",
+		"player.previous":    "P",
+		"player.volumeUp":    "Up",
+		"player.volumeDown":  "Down",
+		"player.seekForward": "Right",
+		"player.seekBack":    "Left",
+		"player.shuffle":     "S",
+		"player.repeat":      "R",
+		"player.mute":        "M",
+
+		// Navigation (Global scope)
+		"nav.search":    "/",
+		"nav.searchAlt": "Ctrl+F",
+		"nav.queue":     "Q",
+
+		// App actions (Global scope, Ctrl modifier)
+		"app.selectAll": "Ctrl+A",
+
+		// Panel-specific (track list)
+		"tracklist.play":   "Enter",
+		"tracklist.delete": "Delete",
+	}
+}
+
+// ApplyDefaults fills any missing bindings with defaults.
+// Existing user customizations are preserved.
+func (c *Config) ApplyDefaults() {
+	if c.Bindings == nil {
+		c.Bindings = DefaultBindings()
+
+		return
+	}
+
+	defaults := DefaultBindings()
+	for action, key := range defaults {
+		if _, exists := c.Bindings[action]; !exists {
+			c.Bindings[action] = key
+		}
+	}
+}
+
+// Validate checks that the config is well-formed.
+func (c *Config) Validate() error {
+	c.ApplyDefaults()
+	// No validation errors possible — any string is a valid binding.
+	// Conflict detection is a frontend UX concern, not a config error.
+	return nil
+}