feat: initial Skeen-CRM AI Agent architecture

- FastAPI + Python 3.12 backend
- Meta WhatsApp Business API client (official)
- OpenAI GPT-4o with function calling
- RAG vector store with pgvector
- ERPNext Frappe REST client
- Celery + Redis async task queue
- PostgreSQL with migrations (Alembic)
- Docker Compose full stack
- Enterprise logging, metrics, health checks

src/api/deps.py

@@ -0,0 +1,36 @@
+"""FastAPI dependency injection providers."""
+
+from typing import AsyncGenerator
+
+from fastapi import Request
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from src.infrastructure.db import AsyncSessionLocal
+from src.infrastructure.redis import RedisCache, get_redis
+
+
+async def get_db_session() -> AsyncGenerator[AsyncSession, None]:
+    """Yield a database session for FastAPI dependency injection."""
+    session = AsyncSessionLocal()
+    try:
+        yield session
+        await session.commit()
+    except Exception:
+        await session.rollback()
+        raise
+    finally:
+        await session.close()
+
+
+async def get_cache() -> AsyncGenerator[RedisCache, None]:
+    """Yield a Redis cache instance."""
+    redis = await get_redis()
+    yield RedisCache(redis)
+
+
+def get_client_ip(request: Request) -> str:
+    """Extract client IP from request, handling proxies."""
+    forwarded = request.headers.get("x-forwarded-for")
+    if forwarded:
+        return forwarded.split(",")[0].strip()
+    return request.client.host if request.client else "unknown"