docs(07-01): complete backend multilanguage foundation plan

.planning/REQUIREMENTS.md

@@ -76,10 +76,10 @@ Requirements for beta-ready release. Each maps to roadmap phases.
 
 - [ ] **I18N-01**: Portal UI fully localized in English, Spanish, and Portuguese (all pages, labels, buttons, error messages)
 - [ ] **I18N-02**: Language switcher accessible from anywhere in the portal — selection persists across sessions
-- [ ] **I18N-03**: AI Employees detect user language and respond accordingly, or use a language configured per agent
-- [ ] **I18N-04**: Agent templates, wizard steps, and onboarding flow are fully translated in all three languages
-- [ ] **I18N-05**: Error messages, validation text, and system notifications are localized
-- [ ] **I18N-06**: Adding a new language requires only translation files, not code changes (extensible i18n architecture)
+- [x] **I18N-03**: AI Employees detect user language and respond accordingly, or use a language configured per agent
+- [x] **I18N-04**: Agent templates, wizard steps, and onboarding flow are fully translated in all three languages
+- [x] **I18N-05**: Error messages, validation text, and system notifications are localized
+- [x] **I18N-06**: Adding a new language requires only translation files, not code changes (extensible i18n architecture)
 
 ## v2 Requirements
 
@@ -172,10 +172,10 @@ Which phases cover which requirements. Updated during roadmap creation.
 | CHAT-05 | Phase 6 | Complete |
 | I18N-01 | Phase 7 | Pending |
 | I18N-02 | Phase 7 | Pending |
-| I18N-03 | Phase 7 | Pending |
-| I18N-04 | Phase 7 | Pending |
-| I18N-05 | Phase 7 | Pending |
-| I18N-06 | Phase 7 | Pending |
+| I18N-03 | Phase 7 | Complete |
+| I18N-04 | Phase 7 | Complete |
+| I18N-05 | Phase 7 | Complete |
+| I18N-06 | Phase 7 | Complete |
 
 **Coverage:**
 - v1 requirements: 25 total (all complete)