implement Clean Architecture and user authentication

- Add LoopFit.Domain with entities (ApplicationUser, Workout, CalorieEntry, VitalData), enums (WorkoutType), and interfaces (IJwtTokenGenerator, IUserRepository, IWorkoutRepository)
- Add LoopFit.Application with auth DTOs, service interfaces, and DI setup
- Add LoopFit.Infrastructure with EF Core DbContext (PostgreSQL), ASP.NET Core Identity, JWT token generation, and repository implementations
- Add AuthController with register/login/me endpoints and JWT Bearer auth
- Add MAUI auth services (AuthService, TokenStorageService) and Login/Register Blazor pages

LoopFit.Web/Components/Layout/NavMenu.razor

@@ -0,0 +1,17 @@
+<div class="top-row ps-3 navbar navbar-dark">
+    <div class="container-fluid">
+        <a class="navbar-brand" href="">LoopFit</a>
+    </div>
+</div>
+
+<input type="checkbox" title="Navigation menu" class="navbar-toggler"/>
+
+<div class="nav-scrollable" onclick="document.querySelector('.navbar-toggler').click()">
+    <nav class="nav flex-column">
+        <div class="nav-item px-3">
+            <NavLink class="nav-link" href="" Match="NavLinkMatch.All">
+                <span class="bi bi-house-door-fill-nav-menu" aria-hidden="true"></span> Home
+            </NavLink>
+        </div>
+    </nav>
+</div>