fix: remove DeepSeek/MiniMax branding, fix glossary visibility, improve translate page UX

- US1: Replace exposed provider names (DeepSeek V3 → IA Express, MiniMax → IA Avancée)
  in legacy_routes.py, remove 52 DeepSeek references from i18n pricing/landing keys,
  add generic modelName key across all 13 languages
- US2: Fix glossary selector filtering (fallback to all glossaries when source lang
  filter returns empty), show templates by default, fix 3 broken presets
  (hvac/construction/automotive → hr/scientific/ecommerce)
- US3: Replace 15 hardcoded French strings with i18n t() calls, increase font sizes
  from 8-9px to 11px, improve text contrast (opacity /20→/40, /25→/45, /30→/50)
- US4: Add missing provider labels in admin ProviderStatus (deepseek, minimax, zai,
  google_cloud, openrouter, openrouter_premium)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/app/admin/ProviderStatus.tsx

@@ -15,10 +15,15 @@ interface ProviderStatusProps {
 
 const PROVIDER_LABELS: Record<string, string> = {
   google: "Google Translate",
+  google_cloud: "Google Cloud",
   deepl: "DeepL",
   ollama: "Ollama (Local)",
   openai: "OpenAI",
-  openrouter: "OpenRouter",
+  openrouter: "IA Essentielle",
+  openrouter_premium: "IA Premium",
+  deepseek: "IA Express",
+  minimax: "IA Avancée",
+  zai: "Grok (xAI)",
 };
 
 const STATUS_CONFIG = {