feat: Extend account feature flag storage (#14947)

# Pull Request Template

## Description

Extends account-level feature flags by adding a second bigint bitset
column, `feature_flags_ext_2`, while preserving the existing
`flag_shih_tzu` feature check and enable/disable APIs. Existing flags
continue to live on `feature_flags`; future flags can opt into the
extension column through `config/features.yml` metadata.

Fixes
[CW-7238](https://linear.app/chatwoot/issue/CW-7238/feature-flag-extension)

## Type of change

- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality not to work as expected)
- [ ] This change requires a documentation update

## How Has This Been Tested?

- `eval "$(rbenv init -)" && RAILS_ENV=test
POSTGRES_DATABASE=chatwoot_test_31a6 bundle exec rspec
spec/models/concerns/featurable_spec.rb spec/models/account_spec.rb
spec/lib/config_loader_spec.rb
spec/controllers/platform/api/v1/accounts_controller_spec.rb
spec/controllers/super_admin/accounts_controller_spec.rb
spec/enterprise/models/account_spec.rb` - 144 examples, 0 failures
- `eval "$(rbenv init -)" && bundle exec rubocop
app/models/concerns/featurable.rb app/models/account.rb
db/migrate/20260706215758_add_feature_flags_ext_2_to_accounts.rb
spec/models/concerns/featurable_spec.rb spec/models/account_spec.rb
spec/lib/config_loader_spec.rb spec/enterprise/models/account_spec.rb` -
7 files inspected, no offenses detected
- `ruby -ryaml -e "features =
YAML.safe_load(File.read('config/features.yml')); abort unless
features.size == 63; puts features.group_by { |f| f['column'] ||
'feature_flags' }.transform_values(&:size).inspect"` - `{"feature_flags"
=> 63}`
- `git diff --check`

## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] I have commented on my code, particularly in hard-to-understand
areas
- [x] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [x] Any dependent changes have been merged and published in downstream
modules

db/migrate/20260706215758_add_feature_flags_ext_2_to_accounts.rb

@@ -0,0 +1,5 @@
+class AddFeatureFlagsExt2ToAccounts < ActiveRecord::Migration[7.0]
+  def change
+    add_column :accounts, :feature_flags_ext_1, :bigint, default: 0, null: false
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.1].define(version: 2026_06_30_000000) do
+ActiveRecord::Schema[7.1].define(version: 2026_07_06_215758) do
   # These extensions should be enabled to support this database
   enable_extension "pg_stat_statements"
   enable_extension "pg_trgm"
@@ -73,6 +73,7 @@ ActiveRecord::Schema[7.1].define(version: 2026_06_30_000000) do
     t.integer "status", default: 0
     t.jsonb "internal_attributes", default: {}, null: false
     t.jsonb "settings", default: {}
+    t.bigint "feature_flags_ext_1", default: 0, null: false
     t.index ["status"], name: "index_accounts_on_status"
   end