Fixes #7–#11: launcher Other tab, ICCCM size hints, icon loading, multi-desktop

Fix #7: Add "Other" catch-all category to the launcher. map_category() now
returns "Other" instead of "" for unrecognized .desktop Categories, and an
"Other" tab is added to the CATS list so those apps are discoverable instead
of silently hidden.

Fix #8: Respect ICCCM WM_NORMAL_HINTS. client_add() reads PMinSize,
PResizeInc, and PBaseSize from the window's size hints. The resize drag
handler in events.c clamps to min_w/min_h and snaps to the
width_inc/height_inc grid, fixing jank in character-cell terminal emulators
(xterm, Alacritty).

Fix #10: Optional freedesktop icon loading via imlib2. The launcher now
parses the Icon= field from .desktop files and attempts to render a PNG icon
from Papirus-Dark (or hicolor fallback). When imlib2 is not present the
existing letter-square is shown unchanged. launcher/Makefile auto-detects
imlib2 via pkg-config and sets -DHAVE_IMLIB2.

Fix #11: True 4-desktop support in the WM. Each Client carries a desktop
field (assigned at map time from wm->cur_desktop). Clicking a workspace
button in the deskbar sends _NET_CURRENT_DESKTOP; the WM now handles it via
wm_switch_desktop() which unmaps frames on the leaving desktop, maps frames
on the arriving desktop, and re-focuses. _NET_WM_DESKTOP is set per window
so the deskbar can filter db_update_apps() to show only current-desktop
windows (sticky windows with desktop 0xFFFFFFFF are always shown).

deskbar/src/deskbar.c

@@ -111,8 +111,14 @@ void db_update_apps(Deskbar *db) {
 
     Atom net_wm_state        = XInternAtom(db->dpy, "_NET_WM_STATE",        False);
     Atom net_wm_state_hidden = XInternAtom(db->dpy, "_NET_WM_STATE_HIDDEN", False);
+    Atom net_wm_desktop      = XInternAtom(db->dpy, "_NET_WM_DESKTOP",      False);
 
     for (unsigned long i = 0; i < n && db->napps < DB_MAX_APPS; i++) {
+        /* only show windows on the current desktop (or sticky: desktop == 0xFFFFFFFF) */
+        long win_desk = ewmh_get_long(db, wins[i], net_wm_desktop);
+        if (win_desk >= 0 && win_desk != (long)db->cur_ws && win_desk != (long)0xFFFFFFFF)
+            continue;
+
         db->apps[db->napps].win       = wins[i];
         db->apps[db->napps].focused   = (wins[i] == (Window)active_win);
         db->apps[db->napps].minimized = 0;
@@ -1285,6 +1291,8 @@ void db_run(Deskbar *db) {
                     db_draw(db);
                 } else if (e.xproperty.atom == db->net_current_desktop) {
                     db_update_workspace(db);
+                    db_update_apps(db);  /* re-filter by new desktop */
+                    db_resize(db);
                     db_draw(db);
                 }
                 break;