refactor: support remote Ollama server in docker-compose

- Remove Ollama service from docker-compose.yml (now external/remote)
- Remove ollama_data volume and network configuration
- Simplify compose to only llm-monitor service
- Use env_file for all configuration from .env
- Make API_PORT dynamic with ${API_PORT:-8000}
- Update env.example with Ollama remote server examples:
  - Local development: http://localhost:11434
  - Remote server: http://ollama.example.com:11434
  - Remote with SSL: https://ollama.example.com
- Improve documentation for remote Ollama setup

This allows deployment against any Ollama server (local or remote).

env.example

@@ -1,10 +1,14 @@
 # LLM Monitor - Environment Configuration Example
-# Copy this file to .env and adjust values for your environment
+# Copia questo file in .env e personalizza per il tuo ambiente
 
 # ===========================================
-# Ollama Configuration
+# Ollama Configuration (Remote Server)
 # ===========================================
-# URL base dell'API Ollama
+# URL base dell'API Ollama (server remoto)
+# Esempi:
+#   - http://localhost:11434              (sviluppo locale)
+#   - http://ollama.example.com:11434     (server remoto)
+#   - https://ollama.example.com          (con SSL)
 OLLAMA_HOST=http://localhost:11434
 
 # Timeout per le richieste a Ollama (secondi)