page: remove load_once and update others

src/ui/page.py

@@ -7,8 +7,6 @@ class Page:
     image: Union[str, Path, None] = None
     can_reload: bool = False
 
-    loaded: bool = False
-
     def id(self):
         return self.__gtype_name__
 
@@ -17,22 +15,14 @@ class Page:
     def load(self):
         '''
         Called before the page is shown.
-        Pages can overwrite this to receive call every time.
-        Returning True means the page can be skipped.
+        Pages can overwrite this to receive a call every time.
+        Specialld handled return values are:
+        "load_next", "load_prev", "prevent_back_navigation".
         '''
-        if not self.loaded:
-            self.loaded = True
-            return self.load_once()
-
-    def load_once(self):
-        '''
-        Called once on first page construction. Used for e.g. filling lists.
-        Special return values: "load_next" (skips page), "prevent_back_navigation"
-        '''
-        return
+        pass
 
     def unload(self):
         '''
         Called before the page is no longer shown. Used for e.g. storing current enrty values.
         '''
-        return
+        pass