Fix 404 error when saving user preferences

Routes using withAuth were creating new unauthenticated PocketBase
clients, causing 404 errors when trying to update records. Modified
withAuth to pass the authenticated pb client to handlers so they can
use it for database operations.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/lib/auth-middleware.test.ts

@@ -113,7 +113,12 @@ describe("withAuth", () => {
     const response = await wrappedHandler(mockRequest);
 
     expect(response.status).toBe(200);
-    expect(handler).toHaveBeenCalledWith(mockRequest, mockUser, undefined);
+    expect(handler).toHaveBeenCalledWith(
+      mockRequest,
+      mockUser,
+      mockPbClient,
+      undefined,
+    );
   });
 
   it("loads auth from cookies before checking authentication", async () => {
@@ -159,7 +164,7 @@ describe("withAuth", () => {
 
     await wrappedHandler(mockRequest, { params: mockParams });
 
-    expect(handler).toHaveBeenCalledWith(mockRequest, mockUser, {
+    expect(handler).toHaveBeenCalledWith(mockRequest, mockUser, mockPbClient, {
       params: mockParams,
     });
   });