fix(frontend): Fix user field name mapping from backend to frontend

Resolved authentication issue where user.id was undefined, causing Epic creation to fail.

Root Cause:
- Backend /api/auth/login returns UserDto with PascalCase fields (Id, Email, etc.)
- Backend /api/auth/me returns JWT claims with camelCase (userId, email, etc.)
- Frontend User type expects camelCase fields (id, email, etc.)
- Previous code directly assigned backend fields without mapping

Changes:
- useLogin: Added field mapping to handle both PascalCase and camelCase
- useCurrentUser: Map userId -> id and tenantSlug -> tenantName
- Both functions now correctly populate user.id for localStorage persistence

Impact:
- Epic creation now works (user.id is correctly set)
- Auth state persists correctly across page reloads
- Consistent user object structure throughout frontend

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

lib/hooks/useAuth.ts

@@ -30,16 +30,20 @@ export function useLogin() {
       tokenManager.setAccessToken(data.accessToken);
       tokenManager.setRefreshToken(data.refreshToken);
 
+      // Map backend field names to frontend User type
+      // Backend returns: { Id, TenantId, Email, FullName, ... }
+      // Frontend expects: { id, tenantId, email, fullName, ... }
+      const backendUser = data.user;
       setUser({
-        id: data.user.id,
+        id: backendUser.id || backendUser.Id, // Handle both casing
-        email: data.user.email,
+        email: backendUser.email || backendUser.Email,
-        fullName: data.user.fullName,
+        fullName: backendUser.fullName || backendUser.FullName,
-        tenantId: data.user.tenantId,
+        tenantId: backendUser.tenantId || backendUser.TenantId,
-        tenantName: data.user.tenantName,
+        tenantName: data.tenant?.name || data.tenant?.Name || 'Unknown',
-        role: data.user.role,
+        role: data.tenant?.role || backendUser.role || 'TenantMember',
-        isEmailVerified: data.user.isEmailVerified,
+        isEmailVerified: backendUser.isEmailVerified ?? backendUser.IsEmailVerified ?? false,
-        createdAt: data.user.createdAt || new Date().toISOString(),
+        createdAt: backendUser.createdAt || backendUser.CreatedAt || new Date().toISOString(),
-        updatedAt: data.user.updatedAt,
+        updatedAt: backendUser.updatedAt || backendUser.UpdatedAt,
       });
 
       router.push('/dashboard');
@@ -95,9 +99,24 @@ export function useCurrentUser() {
     queryKey: ['currentUser'],
     queryFn: async () => {
       const { data } = await apiClient.get(API_ENDPOINTS.ME);
-      setUser(data);
+
+      // Map backend /me response to frontend User type
+      // Backend returns: { userId, tenantId, email, fullName, tenantSlug, tenantRole, role }
+      // Frontend expects: { id, tenantId, email, fullName, tenantName, role, isEmailVerified, createdAt }
+      const mappedUser = {
+        id: data.userId || data.id, // Backend uses 'userId'
+        email: data.email,
+        fullName: data.fullName,
+        tenantId: data.tenantId,
+        tenantName: data.tenantSlug || 'Unknown', // Use tenantSlug as tenantName fallback
+        role: data.tenantRole || data.role || 'TenantMember',
+        isEmailVerified: true, // Assume verified if token is valid
+        createdAt: new Date().toISOString(),
+      };
+
+      setUser(mappedUser);
       setLoading(false);
-      return data;
+      return mappedUser;
     },
     enabled: !!tokenManager.getAccessToken(),
     retry: false,