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>

routes/legacy_routes.py

@@ -167,8 +167,8 @@ async def get_available_providers():
         )
         available.append({
             "id": "deepseek",
-            "label": "DeepSeek V3",
-            "description": "Traduction IA avancée via DeepSeek",
+            "label": "Traduction IA Express",
+            "description": "Traduction IA rapide et optimisée",
             "mode": "llm",
             "tier": "pro",
             "model": model,
@@ -184,8 +184,8 @@ async def get_available_providers():
         )
         available.append({
             "id": "minimax",
-            "label": "MiniMax",
-            "description": "Traduction IA via MiniMax",
+            "label": "Traduction IA Avancée",
+            "description": "Traduction IA haute performance",
             "mode": "llm",
             "tier": "pro",
             "model": model,