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>

src/infrastructure/mod.rs

@@ -3,8 +3,8 @@
 pub mod auth_check;
 pub mod chat;
 pub mod langgraph;
+pub mod litellm;
 pub mod llm;
-pub mod ollama;
 pub mod searxng;
 
 // Server-only modules (Axum handlers, state, configs, DB, etc.)