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/app/project-tasks/page.js

@@ -7,7 +7,7 @@ export default function ProjectTasksPage() {
 		<PageContainer>
 			<PageHeader
 				title="Zadania projektów"
-				description="Przeglądaj i zarządzaj zadaniami wszystkich projektów w ustrukturyzowanym formacie listy"
+				description="---"
 			/>
 			<ProjectTasksList />
 		</PageContainer>