feat: add expose all windows keybinding and Alt-drag window manipulation with floating state tracking

Implement key_expose_all function bound to Alt+Space that unminimizes, unmaximizes, and unfullscreens all windows on current workspace then rearranges. Add floating_before_maximize boolean to Client struct to preserve floating state when toggling maximize. Enable Alt+LeftDrag for moving and Alt+RightDrag for resizing windows from any position with directional cursor support. Increase resize edge detection from 8 to 12 pixels. Add panel.h dependency to keys build target and update shortcut help text with new bindings.

include/dwn.h

@@ -125,6 +125,7 @@ struct Client {
     char title[256];
     char class[64];
     SnapConstraint snap;
+    bool floating_before_maximize;
     unsigned long taskbar_color;
     ColorAnimation title_anim;
     TextGlowAnimation text_glow;
@@ -219,6 +220,17 @@ typedef struct {
     int last_mouse_x;
     int last_mouse_y;
     bool mouse_tracking_initialized;
+
+    Cursor cursor_default;
+    Cursor cursor_resize_top_left;
+    Cursor cursor_resize_top_right;
+    Cursor cursor_resize_bottom_left;
+    Cursor cursor_resize_bottom_right;
+    Cursor cursor_resize_left;
+    Cursor cursor_resize_right;
+    Cursor cursor_resize_top;
+    Cursor cursor_resize_bottom;
+    Cursor cursor_move;
 } DWNState;
 
 #define PHASE_OFFSET_PANEL_BG      0.0f

include/keys.h

@@ -100,6 +100,7 @@ void key_resize_window_up(void);
 void key_resize_window_down(void);
 void key_set_mark(void);
 void key_goto_mark(void);
+void key_expose_all(void);
 
 void tutorial_start(void);
 void tutorial_stop(void);