Add warning for TwelveData plan-restricted tickers (#803)

* Add warning for TwelveData plan-restricted tickers

Fixes #800

- Add Security::PlanRestrictionTracker concern using Rails cache
- Detect plan upgrade errors during Security::Price::Importer sync
- Display amber warning on /settings/hosting with affected tickers
- Include unit tests for the new functionality

* Scope plan restriction cache by provider

Addresses review feedback:
- Cache key now includes provider name to support multiple data providers
- Methods now require provider parameter for proper scoping
- Added tests for provider-scoped restrictions
- Added documentation explaining instance-level API key architecture

* Fix RuboCop array bracket spacing

* Fix empty array bracket spacing

* Move plan upgrade detection to Provider::TwelveData

* Fix provider scoping tests to use direct cache writes

---------

Co-authored-by: mkdev11 <jaysmth689+github@users.noreply.github.com>

app/controllers/settings/hostings_controller.rb

@@ -25,6 +25,7 @@ class Settings::HostingsController < ApplicationController
     if @show_twelve_data_settings
       twelve_data_provider = Provider::Registry.get_provider(:twelve_data)
       @twelve_data_usage = twelve_data_provider&.usage
+      @plan_restricted_securities = Current.family.securities_with_plan_restrictions(provider: "TwelveData")
     end
 
     if @show_yahoo_finance_settings