fix: add comprehensive debugging and validation for avatar uploads

- Add detailed error extraction from API responses
- Validate file content is not empty before saving
- Verify file was actually saved to disk
- Check saved file size matches expectations
- Add extensive logging for debugging upload issues
- Improve error messages with specific details

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

web/src/pages/SettingsPage.tsx

@@ -218,17 +218,24 @@ function SettingsForm({ me, onBack }: { me: MemberRead; onBack: () => void }) {
                   qc.invalidateQueries({ queryKey: ['me'] });
                 } catch (err) {
                   console.error("Upload failed:", err);
+                  let errorMessage = 'Failed to upload avatar. Please try again.';
+                  
                   if (err instanceof Error) {
+                    errorMessage = err.message;
                     if (err.message.includes('413')) {
-                      setError('File too large. Maximum size is 5MB. Please choose a smaller image.');
+                      errorMessage = 'File too large. Maximum size is 5MB. Please choose a smaller image.';
                     } else if (err.message.includes('422')) {
-                      setError('Invalid image file. Please upload a valid image (JPG, PNG, etc.).');
-                    } else {
-                      setError(err.message);
+                      errorMessage = 'Invalid image file. Please upload a valid image (JPG, PNG, etc.).';
+                    }
+                  } else if (typeof err === 'object' && err !== null) {
+                    // Try to extract more details from the error object
+                    console.error("Error details:", JSON.stringify(err));
+                    if (err.status === 422 && err.data && err.data.detail) {
+                      errorMessage = err.data.detail;
                     }
-                  } else {
-                    setError('Failed to upload avatar. Please try again.');
                   }
+                  
+                  setError(errorMessage);
                 } finally {
                   setUploading(false);
                 }