add file validate option

src/app/browser/window/tab/item/identity/gemini/widget/form.rs

@@ -74,6 +74,7 @@ impl Form {
     pub fn is_valid(&self) -> bool {
         match self.list.selected() {
             Value::GENERATE_NEW_AUTH => self.name.is_valid(),
+            Value::IMPORT_PEM => self.file.is_valid(),
             _ => true,
         }
     }

src/app/browser/window/tab/item/identity/gemini/widget/form/file.rs

@@ -4,12 +4,13 @@ use gtk::{
     Button,
 };
 
-use std::rc::Rc;
+use std::{cell::RefCell, rc::Rc};
 
 const LABEL: &str = "Select file..";
 const MARGIN: i32 = 8;
 
 pub struct File {
+    pem: RefCell<Option<String>>,
     pub gobject: Button,
 }
 
@@ -18,6 +19,9 @@ impl File {
 
     /// Create new `Self`
     pub fn new(action: Rc<Action>) -> Self {
+        // Init PEM
+        let pem = RefCell::new(None);
+
         // Init `GObject`
         let gobject = Button::builder()
             .label(LABEL)
@@ -29,7 +33,7 @@ impl File {
         gobject.connect_clicked(move |_| todo!());
 
         // Return activated `Self`
-        Self { gobject }
+        Self { pem, gobject }
     }
 
     // Actions
@@ -42,4 +46,10 @@ impl File {
             self.gobject.grab_focus();
         }
     }
+
+    // Getters
+
+    pub fn is_valid(&self) -> bool {
+        self.pem.borrow().is_some()
+    }
 }