feat(mobile): disable swipe back gesture when there is no back in header (#8876)

close AF-1663, AF-1756

- new global `ModalConfigContext`
- new logic to judge whether inside modal
- render `✕` for PageHeader back if inside modal
- only enable `NavigationGesture` when there is `<` in PageHeader

packages/frontend/apps/ios/App/App/AFFiNEViewController.swift

@@ -5,11 +5,13 @@ class AFFiNEViewController: CAPBridgeViewController {
 
   override func viewDidLoad() {
     super.viewDidLoad()
-    webView?.allowsBackForwardNavigationGestures = true
+    // disable by default, enable manually when there is a "back" button in page-header
+    webView?.allowsBackForwardNavigationGestures = false
   }
   
   override func capacitorDidLoad() {
     bridge?.registerPluginInstance(CookiePlugin())
     bridge?.registerPluginInstance(HashcashPlugin())
+    bridge?.registerPluginInstance(NavigationGesturePlugin())
   }
 }

packages/frontend/apps/ios/App/App/plugins/NavigationGesture/NavigationGesturePlugin.swift

@@ -0,0 +1,32 @@
+import Foundation
+import Capacitor
+
+@objc(NavigationGesturePlugin)
+public class NavigationGesturePlugin: CAPPlugin, CAPBridgedPlugin {
+  public let identifier = "NavigationGesturePlugin"
+  public let jsName = "NavigationGesture"
+  public let pluginMethods: [CAPPluginMethod] = [
+      CAPPluginMethod(name: "isEnabled", returnType: CAPPluginReturnPromise),
+      CAPPluginMethod(name: "enable", returnType: CAPPluginReturnPromise),
+      CAPPluginMethod(name: "disable", returnType: CAPPluginReturnPromise)
+  ]
+  
+  @objc func isEnabled(_ call: CAPPluginCall) {
+    let enabled = self.bridge?.webView?.allowsBackForwardNavigationGestures ?? true
+    call.resolve(["value": enabled])
+  }
+  
+  @objc func enable(_ call: CAPPluginCall) {
+    DispatchQueue.main.sync {
+      self.bridge?.webView?.allowsBackForwardNavigationGestures = true
+      call.resolve([:])
+    }
+  }
+  
+  @objc func disable(_ call: CAPPluginCall) {
+    DispatchQueue.main.sync {
+      self.bridge?.webView?.allowsBackForwardNavigationGestures = false
+      call.resolve([:])
+    }
+  }
+}