feat: add VRAM management for Jean/Ollama switching

- stop_jean(): stops Jean service to free VRAM before Ollama use
- start_jean(): starts Jean service when switching back from Ollama
- unload_ollama(): forces Ollama to unload models before Jean use
- ensure_vram_for_backend(): orchestrates VRAM switching
- Tracks active backend state to avoid unnecessary switches
- Configurable timeouts via environment variables
- Prevents VRAM contention between Jean and Ollama

docker-compose.litellm.yml

@@ -63,7 +63,12 @@ services:
       - JEAN_PROXY_PORT=3012
       - OLLAMA_PROXY_HOST=localhost
       - OLLAMA_PROXY_PORT=3011
+      - OLLAMA_DIRECT_HOST=${OLLAMA_HOST}
+      - OLLAMA_DIRECT_PORT=11434
       - ENABLE_OLLAMA=true
+      - ENABLE_VRAM_MANAGEMENT=true
       - LISTEN_PORT=3014
       - SWITCH_TIMEOUT=90
       - CHECK_INTERVAL=2
+      - JEAN_STOP_TIMEOUT=30
+      - OLLAMA_UNLOAD_TIMEOUT=15