feat: Add automatic favicon fetching for companies (#13013)

## Summary

This Enterprise-only feature automatically fetches a favicon for
companies created with a domain, and adds a batch task to backfill
missing avatars for existing companies. The flow only targets companies
that do not already have an attached avatar, so existing avatars are
left untouched.


## Demo 



https://github.com/user-attachments/assets/d050334e-769f-4e46-b6e7-f7423727a192



## What changed

- Added `Avatar::AvatarFromFaviconJob` to build a Google favicon URL
from the company domain and fetch it through `Avatar::AvatarFromUrlJob`
- Triggered favicon fetching from `Company` with `after_create_commit`
- Added `Companies::FetchAvatarsJob` to batch existing companies that
are missing avatars
- Added `companies:fetch_missing_avatars` under `enterprise/lib/tasks`
- Kept the company-specific implementation inside the Enterprise
boundary
- Stubbed the new favicon request in unrelated specs that now hit this
callback indirectly
- Updated a couple of CI-sensitive specs that were failing due to
callback side effects / reload-safe exception assertions

## How to verify

1. Create a company in Enterprise with a valid domain and no avatar.
2. Confirm that a favicon-based avatar gets attached shortly after
creation.
3. Create another company with a domain and an avatar already attached.
4. Confirm that the existing avatar is not replaced.
5. Run `companies:fetch_missing_avatars`.
6. Confirm that existing companies without avatars get one, while
companies that already have avatars remain unchanged.

## Notes

- This change does not refresh or overwrite existing company avatars
- Favicon fetching only runs for companies with a present domain
- The branch includes the latest `develop`

---------

Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>
Co-authored-by: Sojan Jose <sojan@pepalo.com>

spec/services/account/sign_up_email_validation_service_spec.rb

@@ -20,7 +20,7 @@ RSpec.describe Account::SignUpEmailValidationService, type: :service do
       it 'raises InvalidEmail with invalid message' do
         allow(ValidEmail2::Address).to receive(:new).with(email).and_return(invalid_email_address)
         expect { service.perform }.to raise_error do |error|
-          expect(error).to be_a(CustomExceptions::Account::InvalidEmail)
+          expect(error.class.name).to eq('CustomExceptions::Account::InvalidEmail')
           expect(error.message).to eq(I18n.t('errors.signup.invalid_email'))
         end
       end
@@ -32,7 +32,7 @@ RSpec.describe Account::SignUpEmailValidationService, type: :service do
       it 'raises InvalidEmail with blocked domain message' do
         allow(ValidEmail2::Address).to receive(:new).with(email).and_return(valid_email_address)
         expect { service.perform }.to raise_error do |error|
-          expect(error).to be_a(CustomExceptions::Account::InvalidEmail)
+          expect(error.class.name).to eq('CustomExceptions::Account::InvalidEmail')
           expect(error.message).to eq(I18n.t('errors.signup.blocked_domain'))
         end
       end
@@ -44,7 +44,7 @@ RSpec.describe Account::SignUpEmailValidationService, type: :service do
       it 'raises InvalidEmail with blocked domain message' do
         allow(ValidEmail2::Address).to receive(:new).with(email).and_return(valid_email_address)
         expect { service.perform }.to raise_error do |error|
-          expect(error).to be_a(CustomExceptions::Account::InvalidEmail)
+          expect(error.class.name).to eq('CustomExceptions::Account::InvalidEmail')
           expect(error.message).to eq(I18n.t('errors.signup.blocked_domain'))
         end
       end
@@ -56,7 +56,7 @@ RSpec.describe Account::SignUpEmailValidationService, type: :service do
       it 'raises InvalidEmail with disposable message' do
         allow(ValidEmail2::Address).to receive(:new).with(email).and_return(disposable_email_address)
         expect { service.perform }.to raise_error do |error|
-          expect(error).to be_a(CustomExceptions::Account::InvalidEmail)
+          expect(error.class.name).to eq('CustomExceptions::Account::InvalidEmail')
           expect(error.message).to eq(I18n.t('errors.signup.disposable_email'))
         end
       end