fix: TypeScript errors in avatar implementation

- Remove unnecessary headers parameter from API call
- Fix unused error parameter in onError handler
- Use undefined instead of null for avatar_url removal

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

web/src/pages/SettingsPage.tsx

@@ -129,11 +129,7 @@ function SettingsForm({ me, onBack }: { me: MemberRead; onBack: () => void }) {
                   const formData = new FormData();
                   formData.append('file', file);
                   
-                  const response = await api.post<MemberRead>('/auth/me/avatar', formData, {
-                    headers: {
-                      'Content-Type': 'multipart/form-data'
-                    }
-                  });
+                  const response = await api.post<MemberRead>('/auth/me/avatar', formData);
                   
                   setAvatarUrl(response.avatar_url || '');
                   qc.invalidateQueries({ queryKey: ['me'] });
@@ -192,7 +188,7 @@ function SettingsForm({ me, onBack }: { me: MemberRead; onBack: () => void }) {
               src={avatarUrl} 
               alt="Preview" 
               style={{ width: 48, height: 48, borderRadius: "50%", objectFit: "cover" }}
-              onError={(e) => {
+              onError={() => {
                 console.error("Failed to load avatar:", avatarUrl);
                 // Set to default avatar on error
                 setAvatarUrl(`https://api.dicebear.com/v6/identicon/svg?seed=${me.id}&backgroundType=gradientLinear&size=128`);
@@ -201,7 +197,7 @@ function SettingsForm({ me, onBack }: { me: MemberRead; onBack: () => void }) {
             <button
               onClick={async () => {
                 try {
-                  await updateSettings({ avatar_url: null });
+                  await updateSettings({ avatar_url: undefined });
                   setAvatarUrl("");
                   qc.invalidateQueries({ queryKey: ["me"] });
                 } catch (err) {