fix: use consistent API version in ResolveMemberUrn and add error logging

- Changed hardcoded '202401' to LinkedInApiVersion constant ('202506')
- Added response body logging on /v2/me failure for diagnostics

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: csharpfritz

src/TagzApp.Providers.LinkedIn/LinkedInProvider.cs

@@ -251,15 +251,16 @@ public Task StopAsync()
 
 			using var request = new HttpRequestMessage(HttpMethod.Get, $"{LinkedInApiBase}/v2/me");
 			request.Headers.Add("Authorization", $"Bearer {_configuration.AccessToken}");
-			request.Headers.Add("LinkedIn-Version", "202401");
+			request.Headers.Add("LinkedIn-Version", LinkedInApiVersion);
 			request.Headers.Add("X-Restli-Protocol-Version", "2.0.0");
 
 			var response = await _httpClient.SendAsync(request);
 			Interlocked.Increment(ref _dailyCallCount);
 
 			if (!response.IsSuccessStatusCode)
 			{
-				_logger.LogError("LinkedIn me call failed: {StatusCode} {Reason}", (int)response.StatusCode, response.ReasonPhrase);
+				var errorBody = await response.Content.ReadAsStringAsync();
+				_logger.LogError("LinkedIn /v2/me failed: {StatusCode} {Reason} — {Body}", (int)response.StatusCode, response.ReasonPhrase, errorBody);
 				return null;
 			}