Multi-language support (Spanish priority)

[bgorzelic]

Description

California fire crews include many Spanish-speaking members. Firevector should support multiple languages, starting with Spanish as the first translation target.

Proposed Implementation

i18n Framework

• Use next-intl for Next.js internationalization
• Locale detection: browser language → user preference → default (en)
• URL prefix strategy: /en/dashboard, /es/dashboard

Translation Files

apps/web/messages/
├── en.json
└── es.json

Scope

• All UI text (labels, buttons, navigation, error messages)
• Form field labels and descriptions
• Dashboard stats labels
• LCES checklist labels
• Email templates (verification, reset, welcome)
• Domain terms (EWS, ROS) keep English abbreviations with Spanish descriptions

Language Switcher

• Dropdown in header or settings
• Persist preference in user profile (DB) or localStorage
• Flag icons or language codes (EN / ES)

Acceptance Criteria

• All UI text externalized to translation files
• Spanish translation complete for all user-facing text
• Language switcher in header
• Preference persists across sessions
• Email templates translated
• RTL-ready architecture (for future Arabic, etc.)
• URL-based locale routing works
• Fallback to English for missing translations