feat(org): add LiteLLM usage stats to organization dashboard

Replace mock token usage with real data from LiteLLM free-tier APIs
(global/activity, global/activity/model, global/spend/models). Adds
per-model breakdown table, loading/error states, usage data models
with serde tests, and i18n keys for all five languages.

Also includes: replace Ollama with LiteLLM proxy, update config,
docker-compose, and provider infrastructure.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

assets/i18n/fr.json

@@ -144,6 +144,16 @@
     "email_address": "Adresse e-mail",
     "email_placeholder": "collegue@entreprise.com",
     "send_invite": "Envoyer l'invitation",
+    "total_spend": "Depenses totales",
+    "total_tokens": "Tokens totaux",
+    "model_usage": "Utilisation par modele",
+    "model": "Modele",
+    "tokens": "Tokens",
+    "spend": "Depenses",
+    "usage_unavailable": "Donnees d'utilisation indisponibles",
+    "loading_usage": "Chargement des donnees d'utilisation...",
+    "prompt_tokens": "Tokens d'entree",
+    "completion_tokens": "Tokens de reponse",
     "pricing_title": "Tarifs",
     "pricing_subtitle": "Choisissez le plan adapte a votre organisation"
   },