feat: implement TTS, Document processing, and Memory Service /facts API

- TTS: xtts-v2 integration with voice cloning support
- Document: docling integration for PDF/DOCX/PPTX processing
- Memory Service: added /facts/upsert, /facts/{key}, /facts endpoints
- Added required dependencies (TTS, docling)

services/image-gen-service/requirements.txt

@@ -0,0 +1,8 @@
+fastapi==0.110.0
+uvicorn==0.29.0
+torch
+git+https://github.com/huggingface/diffusers.git
+transformers
+accelerate
+safetensors
+pillow