Add initial project documentation

docs/services/memory-service.md

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+# Memory Service
+
+**Package:** `@nexusai/memory-service`  
+**Location:** `packages/memory-service`  
+**Deployed on:** Mini PC 1 (192.168.0.81)  
+**Port:** 3002
+
+## Purpose
+
+Responsible for all reading and writing of long-term memory. Acts as the
+sole interface to both SQLite and Qdrant — no other service accesses these
+stores directly.
+
+## Dependencies
+
+- `express` — HTTP API
+- `better-sqlite3` — SQLite driver
+- `@qdrant/js-client-rest` — Qdrant vector store client
+- `dotenv` — environment variable loading
+- `@nexusai/shared` — shared utilities
+
+## Environment Variables
+
+| Variable | Required | Default | Description |
+|---|---|---|---|
+| PORT | No | 3002 | Port to listen on |
+| SQLITE_PATH | Yes | — | Path to SQLite database file |
+| QDRANT_URL | No | http://localhost:6333 | Qdrant instance URL |
+
+## Endpoints
+
+| Method | Path | Description |
+|---|---|---|
+| GET | /health | Service health check |
+
+> Further endpoints will be documented as the service is built out.