feat: Bulk actions for contacts (#12763)

Introduces APIs and UI for bulk actions in contacts table. The initial
action available will be assign labels

Fixes: #8536 #12253 

## Screens

<img width="1350" height="747" alt="Screenshot 2025-10-29 at 4 05 08 PM"
src="https://github.com/user-attachments/assets/0792dff5-0371-4b2e-bdfb-cd32db773402"
/>
<img width="1345" height="717" alt="Screenshot 2025-10-29 at 4 05 19 PM"
src="https://github.com/user-attachments/assets/ae510404-c6de-4c15-a720-f6d10cdac25b"
/>

---------

Co-authored-by: Muhsin <muhsinkeramam@gmail.com>
Co-authored-by: iamsivin <iamsivin@gmail.com>
Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>

app/jobs/contacts/bulk_action_job.rb

@@ -0,0 +1,14 @@
+class Contacts::BulkActionJob < ApplicationJob
+  queue_as :medium
+
+  def perform(account_id, user_id, params)
+    account = Account.find(account_id)
+    user = User.find(user_id)
+
+    Contacts::BulkActionService.new(
+      account: account,
+      user: user,
+      params: params
+    ).perform
+  end
+end