fix(dock): remove pointless del svg_w, add warning on trash SVG failure

The del was a no-op (GC handles scope exit). The bare except Exception
hid real rendering errors — now logs at warning level.

src/window/dock/canvas.py

@@ -356,8 +356,8 @@ class DockCanvas(Gtk.DrawingArea):
                 self._trash_pixbuf = Gdk.pixbuf_get_from_surface(
                     surface, 0, 0, size, size
                 )
-                del svg_w
-            except Exception:
+            except Exception as e:
+                logger.warning(f"[canvas] Failed to render trash SVG: {e}")
                 self._trash_pixbuf = self._get_pixbuf("user-trash", size)
 
         existing = self.model.get_by_id("trash")