[Bug] Cannot resize window on macOS

### Bug Description

The AppFlowy window cannot be resized on macOS. The resize cursor does not appear when hovering over window edges, and dragging from any corner or edge has no effect.

### How to Reproduce

1. Install AppFlowy on macOS
2. Launch the app
3. Attempt to resize the window by dragging from any edge or corner

### Expected Behavior

The window should be resizable like any standard macOS application window — dragging from edges/corners should resize the window.

### Operating System

macOS

### AppFlowy Version(s)

Latest (0.11.x)

### Code Analysis

I investigated the codebase and found:

- **`MainMenu.xib`** correctly has `resizable="YES"` in the `windowStyleMask`
- **`MainFlutterWindow.swift`** inserts `.fullSizeContentView` but does NOT remove `.resizable` from `styleMask`
- **`window_manager` package** (custom fork at 0.4.3) doesn't have a `resizable` option in `WindowOptions`
- The Flutter `windows.dart` startup task initializes the window with `window_manager.waitUntilReadyToShow()` on macOS

Despite the window being configured as resizable at both the XIB and native Swift level, the window is not resizable at runtime. This suggests a runtime issue, possibly related to how the Flutter view interacts with native macOS window chrome (the Flutter content view may be intercepting edge mouse events).

### Screenshots

_No response_

### Additional Context

_No response_