Address identity review feedback

Author: Copilot

app/models/user.rb

@@ -348,8 +348,10 @@ def merge(*others)
       other_profiles = others.map(&:profile)
       others.each do |other|
         other.identities.each do |identity|
-          existing_identity = identities.find_by(provider: identity.provider, uid: identity.uid)
-          if existing_identity
+          existing_identity = if identity.uid.present?
+                                identities.find_by(provider: identity.provider, uid: identity.uid)
+                              end
+          if existing_identity.present?
             identity.destroy
           else
             identity.update!(user: self)

app/views/identities/index.html.erb

@@ -20,8 +20,7 @@
           <td><%= identity.uid.presence || content_tag(:span, 'Not set', class: 'empty') %></td>
           <td>
             <%= link_to 'Remove', user_identity_path(@user, identity),
-                        method: :delete,
-                        data: { confirm: 'Are you sure you want to remove this identity?' },
+                        data: { turbo_method: :delete, turbo_confirm: 'Are you sure you want to remove this identity?' },
                         class: 'btn btn-danger btn-sm' %>
           </td>
         </tr>

db/migrate/20260723102000_create_identities.rb

@@ -20,6 +20,21 @@ def change
           ON CONFLICT (provider, uid) DO NOTHING
         SQL
       end
+
+      dir.down do
+        execute <<~SQL
+          UPDATE users
+          SET provider = source.provider,
+              uid = source.uid
+          FROM (
+            SELECT DISTINCT ON (user_id) user_id, provider, uid
+            FROM identities
+            ORDER BY user_id, created_at ASC, id ASC
+          ) AS source
+          WHERE users.id = source.user_id
+            AND (users.provider IS NULL OR users.provider = '')
+        SQL
+      end
     end
   end
 end