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

.env.example

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+# =============================================================================
+# FASTAPI APPLICATION
+# =============================================================================
+APP_NAME=Skeen-CRM-Agent
+APP_ENV=development
+DEBUG=true
+LOG_LEVEL=INFO
+SECRET_KEY=change-me-in-production-skeen-2024
+
+# =============================================================================
+# SERVER
+# =============================================================================
+HOST=0.0.0.0
+PORT=8000
+
+# =============================================================================
+# DATABASE (PostgreSQL + pgvector)
+# =============================================================================
+DATABASE_URL=postgresql+asyncpg://skeen:skeen123@localhost:5432/skeen_crm
+DATABASE_POOL_SIZE=20
+DATABASE_MAX_OVERFLOW=10
+
+# =============================================================================
+# REDIS
+# =============================================================================
+REDIS_URL=redis://localhost:6379/0
+
+# =============================================================================
+# META / WHATSAPP BUSINESS API (Oficial)
+# =============================================================================
+META_API_VERSION=v18.0
+META_ACCESS_TOKEN=EAAXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+META_PHONE_NUMBER_ID=123456789012345
+META_BUSINESS_ACCOUNT_ID=987654321098765
+META_WEBHOOK_VERIFY_TOKEN=skeen-webhook-verify-token-2024
+META_APP_SECRET=your-app-secret-for-signature-verification
+
+# =============================================================================
+# OPENAI
+# =============================================================================
+OPENAI_API_KEY=sk-xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+OPENAI_MODEL=gpt-4o
+OPENAI_EMBEDDING_MODEL=text-embedding-3-small
+OPENAI_TEMPERATURE=0.3
+OPENAI_MAX_TOKENS=1500
+
+# =============================================================================
+# RAG / VECTOR STORE
+# =============================================================================
+VECTOR_DIMENSION=1536
+RAG_TOP_K=5
+RAG_SIMILARITY_THRESHOLD=0.75
+
+# =============================================================================
+# ERPNEXT INTEGRATION
+# =============================================================================
+ERPNEXT_BASE_URL=https://skeen.erpnext.com
+ERPNEXT_API_KEY=xxxxxxxxxxxxxxxx
+ERPNEXT_API_SECRET=xxxxxxxxxxxxxxxx
+ERPNEXT_VERIFY_SSL=true
+
+# =============================================================================
+# CELERY
+# =============================================================================
+CELERY_BROKER_URL=redis://localhost:6379/1
+CELERY_RESULT_BACKEND=redis://localhost:6379/2
+CELERY_WORKER_CONCURRENCY=4
+
+# =============================================================================
+# MONITORING
+# =============================================================================
+ENABLE_METRICS=true
+SENTRY_DSN=