feat: Add memory system with SQLite + ChromaDB hybrid storage

- memory_store.py: User-isolated observation storage with vector embeddings
- New endpoints: /memory/save, /memory/query, /memory/get, /memory/timeline
- Progressive disclosure pattern for token-efficient retrieval
- Updated Dockerfile to ROCm 7.2 nightly

app/requirements.txt

@@ -0,0 +1,11 @@
+# PyTorch ROCm installed separately in Dockerfile
+fastapi>=0.104.0
+uvicorn[standard]>=0.24.0
+chromadb>=0.4.0
+sentence-transformers>=2.2.0
+pdfplumber>=0.10.0
+python-docx>=1.0.0
+python-multipart>=0.0.6
+httpx>=0.25.0
+pandas>=2.1.0
+openpyxl>=3.1.0