Add Dutch (nl) translations for UI and models (#702)

* Add Dutch (nl) translations for UI and models

Added comprehensive Dutch translation files for models, views, mailers, and Doorkeeper, covering accounts, categories, admin, and more. Updated languages_helper.rb to include 'nl' as a supported language. Improved capitalization and consistency in existing Dutch date and number formats.

* ai sugestions

* nitpick fix

* Fix Dutch translations and improve consistency

Corrected minor issues and improved consistency in Dutch locale files, including fixing typos, updating terminology (e.g., 'Self-Hosting' to 'Zelfhosting', 'Provider selectie' to 'Providerselectie'), and ensuring proper formatting. No functional changes were made; this commit only affects translation files.

* Update Dutch translations for product name and pluralization

Replaced hardcoded product names with %{product_name} in password reset and API key views for improved reusability. Updated wallet setup message in CoinStats item model to support correct Dutch pluralization.

* Update nl.yml

config/locales/models/user/nl.yml

@@ -0,0 +1,20 @@
+---
+nl:
+  activerecord:
+    attributes:
+      user:
+        email: Email
+        family: Familie
+        family_id: Familie
+        first_name: Voornaam
+        last_name: Achternaam
+        password: Wachtwoord
+        password_confirmation: Bevestiging wachtwoord
+    errors:
+      models:
+        user:
+          attributes:
+            base:
+              cannot_deactivate_admin_with_other_users: Admin kan account niet verwijderen terwijl andere gebruikers aanwezig zijn. Verwijder eerst alle leden.
+            profile_image:
+              invalid_file_size: bestandsgrootte moet minder zijn dan %{max_megabytes} MB