Refactor project tasks page and navigation components

- Updated the description in ProjectTasksPage to a placeholder.
- Commented out the display of assigned email in ProjectTasksList.
- Removed the dashboard link from the navigation items.
- Changed the main link in the navigation to point to projects instead of the dashboard.
- Commented out the LanguageSwitcher and user role display in the navigation.
- Translated "Project Location" to "Lokalizacja projektu" in ProjectMap.
- Commented out the instruction for using the layer control in ProjectMap.
- Removed the label "Coordinates:" from the coordinates display in ProjectMap.
- Updated project and contract subtitles in translations to placeholders.
- Added a new empty validation schema file.

src/components/ProjectTasksList.js

@@ -304,9 +304,9 @@ export default function ProjectTasksList() {
 				{task.assigned_to_name ? (
 					<div>
 						<div className="font-medium">{task.assigned_to_name}</div>
-						<div className="text-xs text-gray-500">
+						{/* <div className="text-xs text-gray-500">
 							{task.assigned_to_email}
-						</div>
+						</div> */}
 					</div>
 				) : (
 					<span className="text-gray-400 italic">{t("projects.unassigned")}</span>