feat(editor): FaiEditorStyle + frosted glass panel + pattern/zoom dropdowns

Visual-effect knobs (FaiEditorStyle) the host can override —
distinct from ColorScheme, which stays orthogonal. Today
Studio passes it through FlowEditorPage's new style:
parameter; tomorrow a theme plugin can ship both colours and
effects in one move.

Two presets ship today: modern (frosted glass, gradient
backdrop, animated flow, shadowed nodes — the default) and
minimal (everything off, flat surfaces — accessibility /
reduce-motion / low-spec).

Properties panel rebuilt as a floating sidebar with
BackdropFilter blur when glass-style is on; falls back to
the pre-0.7 flush-divider layout under solid style.

Pattern + zoom controls promoted to PopupMenuButton dropdowns
so operators reach a specific zoom level / pattern in one
click instead of cycling.

Bumps fai_studio_flow_editor to 0.8.0.

Signed-off-by: flemming-it <sf@flemming.it>

lib/src/widgets/flow_node.dart

@@ -130,6 +130,11 @@ class FlowNode extends StatelessWidget {
   /// Delete / Disconnect inputs etc.).
   final void Function(Offset globalPos)? onContextMenu;
 
+  /// Whether to paint the layered drop shadows under the
+  /// node. Off = flat-design feel; on = depth. Driven by
+  /// the active editor style.
+  final bool elevated;
+
   /// Live status from the most recent run, when this node is
   /// a step. Coloured dot in the header so the operator can
   /// glance at the canvas and see what's running.
@@ -151,6 +156,7 @@ class FlowNode extends StatelessWidget {
     this.onDrag,
     this.onDragEnd,
     this.onContextMenu,
+    this.elevated = true,
   });
 
   @override
@@ -189,19 +195,25 @@ class FlowNode extends StatelessWidget {
             // inner shadow + a softer outer halo. Selected
             // nodes get a coloured accent halo on top so the
             // selection state reads from across the canvas.
-            boxShadow: [
-              BoxShadow(
-                color: Colors.black.withValues(alpha: selected ? 0.32 : 0.18),
-                blurRadius: selected ? 18 : 10,
-                offset: const Offset(0, 4),
-              ),
-              if (selected)
-                BoxShadow(
-                  color: accent.withValues(alpha: 0.30),
-                  blurRadius: 24,
-                  spreadRadius: 1,
-                ),
-            ],
+            // When the active style turns elevation off, we
+            // drop the shadows entirely for a flat-design look.
+            boxShadow: elevated
+                ? [
+                    BoxShadow(
+                      color: Colors.black.withValues(
+                        alpha: selected ? 0.32 : 0.18,
+                      ),
+                      blurRadius: selected ? 18 : 10,
+                      offset: const Offset(0, 4),
+                    ),
+                    if (selected)
+                      BoxShadow(
+                        color: accent.withValues(alpha: 0.30),
+                        blurRadius: 24,
+                        spreadRadius: 1,
+                      ),
+                  ]
+                : null,
           ),
           child: ClipRRect(
             borderRadius: BorderRadius.circular(FaiRadius.md),