fix: Render all account limit fields (#13435)

## Bug Explanation
- The Super Admin limits form renders inputs by iterating the keys of
`account.limits`.
- When `account.limits` was present, `AccountLimitsField#to_s` returned
only that hash (no defaults).
- On save, `SuperAdmin::AccountsController` compacts the limits hash,
removing blank keys.
- Result: if only one key (e.g., `agents`) was saved, the other keys
were missing from the hash and their fields disappeared on the next
render.

## Fix
- Always start from a defaults hash of all expected limit keys and merge
in any saved overrides.
- This keeps the UI stable and ensures all limit inputs remain visible
even when the stored hash is partial.
- Upgraded meta_request to `0.8.5` to stop a dev‑only `SystemStackError`
caused by JSON‑encoding ActiveRecord::Transaction in Rails 7.2. No
production behavior changes.

## Reproduction Steps
1. In Super Admin, edit an account and set only `agents` in the limits;
leave other limit fields blank and save.
2. Re-open the same account in Super Admin.
3. Observe that only `agents` is rendered and other limit fields are
missing.

## Testing
- Tested on UI

---------

Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>

Gemfile.lock

@@ -541,9 +541,9 @@ GEM
       net-smtp
     marcel (1.0.4)
     maxminddb (0.1.22)
-    meta_request (0.8.3)
+    meta_request (0.8.5)
       rack-contrib (>= 1.1, < 3)
-      railties (>= 3.0.0, < 8)
+      railties (>= 3.0.0, < 9)
     method_source (1.1.0)
     mime-types (3.4.1)
       mime-types-data (~> 3.2015)

enterprise/app/fields/account_limits_field.rb

@@ -2,6 +2,9 @@ require 'administrate/field/base'
 
 class AccountLimitsField < Administrate::Field::Base
   def to_s
-    data.present? ? data.to_json : { agents: nil, inboxes: nil, captain_responses: nil, captain_documents: nil, emails: nil }.to_json
+    defaults = { agents: nil, inboxes: nil, captain_responses: nil, captain_documents: nil, emails: nil }
+    overrides = (data.presence || {}).to_h.symbolize_keys.compact
+
+    defaults.merge(overrides).to_json
   end
 end