feat: add volume save/restore on failure/unload

On the first failed unlock attempt, save the current system volume and
mute state then set volume to maximum unmuted; restore on g_module_unload.
A lock file under XDG_RUNTIME_DIR prevents double-acquisition when
multiple gtklock windows are active.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

crates/ahfail-gtklock/src/handler.rs

@@ -56,6 +56,13 @@ impl WindowHandler {
             }
             println!("[ahfail] Error label changed to: '{}'", text_str);
 
+            MODULE_STATE.with(|s| {
+                let mut st = s.borrow_mut();
+                if st.volume_state.is_none() {
+                    st.volume_state = ahfail_ui::volume::save_and_set_max();
+                }
+            });
+
             MODULE_STATE.with(|state| {
                 let state = state.borrow();
                 if let (Some(animation), Some(audio_uri)) = (&state.animation, &state.audio_uri) {

crates/ahfail-gtklock/src/lib.rs

@@ -136,8 +136,12 @@ pub unsafe extern "C" fn on_idle_show(_gtklock: *mut GtkLock) {}
 pub unsafe extern "C" fn g_module_unload(_module: *mut c_void) {
     MODULE_STATE.with(|state| {
         let mut state = state.borrow_mut();
+        if let Some(vs) = state.volume_state.take() {
+            ahfail_ui::volume::restore(vs);
+        }
         state.animation = None;
         state.audio_uri = None;
         state.config.deadzone = None;
+        state.volume_state = None;
     });
 }

crates/ahfail-gtklock/src/state.rs

@@ -7,6 +7,7 @@ pub struct ModuleState {
     pub animation: Option<gdk_pixbuf::PixbufAnimation>,
     pub audio_uri: Option<String>,
     pub config: ModuleConfig,
+    pub volume_state: Option<ahfail_ui::volume::VolumeState>,
 }
 
 pub struct WindowData {
@@ -22,5 +23,6 @@ thread_local! {
         animation: None,
         audio_uri: None,
         config: ModuleConfig { deadzone: None },
+        volume_state: None,
     }) };
 }