i18n(modules): add nav.intro translations for 13 locales

Follow-up to 8c6dfb96: the original i18n fix only added the
intro key to en.yml, relying on Rails fallback for the other
13 layout locales. Per the same review feedback from @jjmata + @codex
on #1955, leaving non-English locales without an explicit
translation regresses user-facing copy whenever the fallback chain
isn't configured to land on en.

Adds intro: per locale, alphabetized between home: and reports:.
Translations chosen:
- ca / nb / nl: Intro (common anglicism)
- de: Einführung
- es: Introducción
- fr: Introduction
- hu: Bemutató
- pl: Wstęp
- pt-BR: Introdução
- ro: Introducere
- tr: Giriş
- zh-CN: 介绍
- zh-TW: 介紹

Translators can refine on their next pass.

config/locales/views/layout/ca.yml

@@ -6,6 +6,7 @@ ca:
         assistant: Assistent
         budgets: Pressupostos
         home: Inici
+        intro: Intro
         reports: Informes
         transactions: Transaccions
       privacy_mode: Commuta el mode de privadesa

config/locales/views/layout/de.yml

@@ -8,6 +8,7 @@ de:
         assistant: Assistent
         budgets: Budgets
         home: Startseite
+        intro: Einführung
         reports: Berichte
         transactions: Transaktionen
     auth:

config/locales/views/layout/es.yml

@@ -8,6 +8,7 @@ es:
         assistant: Asistente
         budgets: Presupuestos
         home: Inicio
+        intro: Introducción
         reports: Informes
         transactions: Transacciones
     auth:

config/locales/views/layout/fr.yml

@@ -8,6 +8,7 @@ fr:
         assistant: Assistant
         budgets: Budgets
         home: Accueil
+        intro: Introduction
         reports: Rapports
         transactions: Transactions
     auth:

config/locales/views/layout/hu.yml

@@ -8,6 +8,7 @@ hu:
         assistant: Asszisztens
         budgets: Költségvetések
         home: Kezdőlap
+        intro: Bemutató
         reports: Jelentések
         transactions: Tranzakciók
     auth:

config/locales/views/layout/nb.yml

@@ -8,6 +8,7 @@ nb:
         assistant: Assistent
         budgets: Budsjett
         home: Hjem
+        intro: Intro
         reports: Rapporter
         transactions: Transaksjoner
     auth:

config/locales/views/layout/nl.yml

@@ -8,6 +8,7 @@ nl:
         assistant: Assistent
         budgets: Budgetten
         home: Startpagina
+        intro: Intro
         reports: Rapporten
         transactions: Transacties
     auth:

config/locales/views/layout/pl.yml

@@ -8,6 +8,7 @@ pl:
         assistant: Asystent
         budgets: Budżety
         home: Strona główna
+        intro: Wstęp
         reports: Raporty
         transactions: Transakcje
     auth:

config/locales/views/layout/pt-BR.yml

@@ -8,6 +8,7 @@ pt-BR:
         assistant: Assistente
         budgets: Orçamentos
         home: Início
+        intro: Introdução
         reports: Relatórios
         transactions: Transações
     auth.sign_up:

config/locales/views/layout/ro.yml

@@ -8,6 +8,7 @@ ro:
         assistant: Asistent
         budgets: Bugete
         home: Acasă
+        intro: Introducere
         reports: Rapoarte
         transactions: Tranzacții
     auth:

config/locales/views/layout/tr.yml

@@ -8,6 +8,7 @@ tr:
         assistant: Asistan
         budgets: Bütçeler
         home: Ana Sayfa
+        intro: Giriş
         reports: Raporlar
         transactions: İşlemler
     auth:

config/locales/views/layout/zh-CN.yml

@@ -9,6 +9,7 @@ zh-CN:
         assistant: 智能助手
         budgets: 预算管理
         home: 首页
+        intro: 介绍
         reports: 财务报告
         transactions: 交易记录
     auth:

config/locales/views/layout/zh-TW.yml

@@ -8,6 +8,7 @@ zh-TW:
         assistant: 助手
         budgets: 預算
         home: 首頁
+        intro: 介紹
         reports: 報表
         transactions: 交易紀錄
     auth: