Polish localization: complete translations, pluralization fixes, and reusable locale audit tooling (#1356)

* Add production-ready Polish localization and reusable locale audit tooling

- add and update Polish locale files across models, views, mailers, and shared translations
- add runtime rails-i18n dependency and Polish locale support in language helper
- add regression coverage for Polish pluralization and locale-aware money formatting
- introduce reusable locale audit script for any locale plus backward-compatible PL wrapper
- add localization audit docs and generated PL readiness/pluralization reports
- resolve one/few/many/other pluralization consistency for Polish locales

* Fix Polish locale review feedback

* Fix locale compatibility regressions

* Polish locale typo pass and wrapper cleanup

* Final language improvements and test isolation for Polish locales

- Improved partial_success wording in SnapTrade with proper noun inflection
- Fixed typos: Pomin → Pomiń in Mercury and LunchFlow items
- Isolated I18n backend state in polish_pluralization_test to prevent test coupling

* Fix code review comments in locale audit scripts

- Use RbConfig.ruby instead of 'ruby' to ensure consistent interpreter
- Remove Symbol from permitted_classes and explicitly allow CLDR plural symbols (one, few, many, other) in YAML loading

* Simplify i18n flow and align locale interpolation keys

* Remove locale audit scripts and localization docs

config/locales/views/shared/pl.yml

@@ -0,0 +1,15 @@
+---
+pl:
+  shared:
+    confirm_modal:
+      accept: Potwierdź
+      body_html: "<p>Nie będzie można cofnąć tej decyzji</p>"
+      cancel: Anuluj
+      title: Czy na pewno?
+    money_field:
+      label: Kwota
+    syncing_notice:
+      syncing: Synchronizowanie danych kont...
+    require_admin: "Tę akcję mogą wykonać tylko administratorzy"
+    trend_change:
+      no_change: "bez zmian"