✨ feat(mana-llm): add central LLM abstraction service

Python/FastAPI service providing unified OpenAI-compatible API for
Ollama and cloud LLM providers (OpenRouter, Groq, Together).

Features:
- Chat completions with streaming (SSE)
- Vision/multimodal support
- Embeddings generation
- Multi-provider routing (provider/model format)
- Prometheus metrics
- Optional Redis caching

services/mana-llm/src/utils/cache.py

@@ -0,0 +1,85 @@
+"""Redis caching utilities (optional)."""
+
+import hashlib
+import json
+import logging
+from typing import Any
+
+from src.config import settings
+
+logger = logging.getLogger(__name__)
+
+# Redis client (lazy initialized)
+_redis_client = None
+
+
+async def get_redis_client():
+    """Get or create Redis client."""
+    global _redis_client
+
+    if _redis_client is not None:
+        return _redis_client
+
+    if not settings.redis_url:
+        return None
+
+    try:
+        import redis.asyncio as redis
+
+        _redis_client = redis.from_url(settings.redis_url)
+        # Test connection
+        await _redis_client.ping()
+        logger.info(f"Connected to Redis at {settings.redis_url}")
+        return _redis_client
+    except Exception as e:
+        logger.warning(f"Failed to connect to Redis: {e}")
+        return None
+
+
+def generate_cache_key(prefix: str, data: dict[str, Any]) -> str:
+    """Generate a cache key from request data."""
+    # Serialize and hash the data for consistent key
+    serialized = json.dumps(data, sort_keys=True)
+    hash_value = hashlib.sha256(serialized.encode()).hexdigest()[:16]
+    return f"mana-llm:{prefix}:{hash_value}"
+
+
+async def get_cached(key: str) -> dict[str, Any] | None:
+    """Get cached value by key."""
+    client = await get_redis_client()
+    if client is None:
+        return None
+
+    try:
+        value = await client.get(key)
+        if value:
+            return json.loads(value)
+    except Exception as e:
+        logger.warning(f"Cache get failed: {e}")
+
+    return None
+
+
+async def set_cached(key: str, value: dict[str, Any], ttl: int | None = None) -> bool:
+    """Set cached value with optional TTL."""
+    client = await get_redis_client()
+    if client is None:
+        return False
+
+    try:
+        ttl = ttl or settings.cache_ttl
+        serialized = json.dumps(value)
+        await client.setex(key, ttl, serialized)
+        return True
+    except Exception as e:
+        logger.warning(f"Cache set failed: {e}")
+        return False
+
+
+async def close_redis() -> None:
+    """Close Redis connection."""
+    global _redis_client
+
+    if _redis_client is not None:
+        await _redis_client.aclose()
+        _redis_client = None