Add 6 desktop features: workspace shortcuts, Exposé, deskbar icons, notifications, screen lock, move-to-desktop

- Super+1-4: switch virtual desktop; Super+Shift+1-4: move focused window to desktop N
- Super+Space: Exposé window overview (tiled grid), click to select, Escape to cancel
- wm/src/expose.c: expose_show/expose_hide using ceil(sqrt) grid layout with saved/restored geometry
- client_move_to_desktop(): moves window between desktops, fires _NET_WM_DESKTOP update
- on_client_message: handles _NET_WM_DESKTOP to move windows from external requests
- deskbar: optional imlib2 app icon rendering (Papirus-Dark → Papirus → hicolor → pixmaps fallback)
- deskbar: XGetClassHint populates cls field for better icon lookup
- deskbar: context menu extended with separator + "→ Desktop 1-4" items via _NET_WM_DESKTOP
- orionnotify/: freedesktop.org notification daemon (libdbus-1), stacks up to 5 popups top-right
- orionlock/: PAM-authenticated fullscreen screen lock with clock, date, password dots
- Lock Screen menu item wired to orionlock
- Root Makefile includes orionnotify and orionlock targets

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GHiBQKPfUoaJgCKuA9op1H

wm/include/wm.h

@@ -82,6 +82,9 @@ typedef struct Client {
     int min_w, min_h;          /* PMinSize */
     int inc_w, inc_h;          /* PResizeInc — 0 means no constraint */
     int base_w, base_h;        /* PBaseSize — baseline for increment calc */
+    /* Exposé saved geometry */
+    int exp_x, exp_y;
+    unsigned exp_w, exp_h;
     struct Client *next;
 } Client;
 
@@ -141,6 +144,11 @@ typedef struct WM {
     Window swl_wins[64];
     char   swl_titles[64][128];
     int    swl_mini[64];           /* 1 if corresponding entry is minimized */
+
+    /* Exposé window overview */
+    int    expose_active;
+    int    expose_count;
+    Window expose_wins[64];        /* frames shown in overview */
 } WM;
 
 /* core */
@@ -163,6 +171,7 @@ void    client_toggle_maximize(WM *wm, Client *c);
 void    client_snap_left(WM *wm, Client *c);
 void    client_snap_right(WM *wm, Client *c);
 void    client_set_wm_state(WM *wm, Client *c, long state);
+void    client_move_to_desktop(WM *wm, Client *c, int new_desk);
 
 /* drawing */
 void          frame_draw(WM *wm, Client *c);
@@ -190,6 +199,10 @@ void switcher_prev(WM *wm);
 void switcher_hide(WM *wm, int commit);
 void switcher_draw(WM *wm);
 
+/* exposé */
+void expose_show(WM *wm);
+void expose_hide(WM *wm, Window selected_frame);
+
 /* events */
 void on_map_request(WM *wm, XMapRequestEvent *e);
 void on_unmap_notify(WM *wm, XUnmapEvent *e);